The Clinical Genome Resource (ClinGen) Familial Hypercholesterolemia Variant Curation Expert Panel consensus guidelines for LDLR variant classification

Correlation between clinical classification and genetic analysis of familial hypercholesterolemia in premature coronary artery disease in a cohort of Egyptian patients

BACKGROUND

Familial Hypercholesterolemia (FH) is a major risk factor for premature Coronary Artery Disease (CAD). Genetic testing is the gold standard for FH diagnosis. The purpose of this Observational Analytical Cross-sectional study was to estimate the proportion of genetically confirmed Familial Hypercholesterolemia in Patients with premature Coronary Artery Disease in a cohort of Egyptian patients.

METHODS

Next generation sequencing (NGS) was conducted for 7 genes (LDLR, PCSK9, APOB, APOE, ABCG5, ABCG8 and LDLRAP1) commonly associated with FH in 94 patients with Premature CAD from 2 tertiary hospitals in Cairo and Alexandria, Egypt. Individuals were clinically assessed using the Dutch Lipid Network criteria and genetically-confirmed FH prevalence was analyzed.

RESULTS

Fourteen patients had pathogenic or likely pathogenic mutations in LDLR, APOB, PCSK9 and LDLRAP1 genes. Three patients had homozygous autosomal dominant FH and another 3 patients had autosomal recessive hypercholesterolemia. In addition, 10 patients had rare variants of uncertain significance in LDLR, APOB, APOE, ABCG5 and ABCG8 genes.

CONCLUSIONS

The prevalence of genetically confirmed FH in premature CAD (PCAD) patients in this study was found to be 14.89%. The Dutch Lipid Clinic Network (DLCN) scoring system is suggested as a good screening tool for familial hypercholesterolemia but confirmatory genetic testing is essential for the accurate diagnosis and management of the patients. In Egypt, the high rate of consanguinity contributes to the high prevalence of both homozygous autosomal dominant and recessive FH.

Role of Next-Generation Sequencing in Diagnosis of Familial Hypercholesterolemia in Serbia

Objectives: Familial hypercholesterolemia (FH) is an autosomal dominant disorder of lipid metabolism characterized by high levels of low-density lipoprotein (LDL). This study aimed to identify variants in the LDLR, APOB, PCSK9 and LDLRAP1 genes and to identify the genotype-phenotype correlation in Serbian FH patients. Method: This study included a total of 101 patients suspected of having FH based on clinical criteria. Genetic analysis was performed by the next-generation sequencing (NGS) method. Results: An overall mutation detection rate of 43.6% was achieved. Thirteen distinct variants were detected in the LDLR gene (93.2%). The most frequently observed variant was c.858C>A p.(Ser286Arg), which was present in 26% of the LDLR-positive patients. Additional variants were detected in the APOB gene. No pathogenic variants were detected in the PCSK9 or LDLRAP1 genes. Comparing genetically FH-positive and FH-negative patients, statistical significance was observed in terms of age (p < 0.001), total cholesterol (TC) (p < 0.001), low-density-lipoprotein cholesterol (LDL-C) (p < 0.001) and triglyceridemia (p < 0.001). Conclusions: This study represents the first insight into the genetic basis of FH in Serbia. Taking into consideration that variants were detected in more than one gene and that the variants in the LDLR gene were distributed across nearly all exons, the FH diagnostics in Serbia ought to be based on NGS methodology.

Navigating variants of uncertain significance in genetic dyslipidemia: how to assess and counsel patients

PURPOSE OF REVIEW

Genetic testing has become an integral component of clinical care when an inherited condition is suspected. However, the interpretation of variants identified with this testing can be nuanced. Variants of uncertain significance (VUS) are variants for which there is not enough data currently available to determine if the variant is causal for disease (i.e. pathogenic) or is benign. VUS can exist on a spectrum with some leaning towards suspected pathogenicity and others leaning towards likely benign. Clinician understanding of variant interpretation can improve clinical care by providing more context around how suspicious a VUS is, determining whether additional steps should be taken to further evaluate the variant in question, and ensuring patient understanding of these results.

RECENT FINDINGS

Research on this topic highlights the complexities around VUS interpretation and counseling. VUS are not static: interpretations of pathogenicity change as new information is uncovered.

SUMMARY

This review aims to summarize this literature and provide insight into variant interpretation, practical steps clinicians can take to further assess a VUS, and considerations when counseling patients on these results.

Functional interrogation of cellular Lp(a) uptake by genome-scale CRISPR screening

BACKGROUND AND AIMS

An elevated level of lipoprotein(a), or Lp(a), in the bloodstream has been causally linked to the development of atherosclerotic cardiovascular disease and calcific aortic valve stenosis. Steady state levels of circulating lipoproteins are modulated by their rate of clearance, but the identity of the Lp(a) uptake receptor(s) has been controversial.

METHODS

We performed a genome-scale CRISPR screen to functionally interrogate all potential Lp(a) uptake regulators in HuH7 cells. Screen validation was performed by single gene disruption and overexpression. Direct binding between purified lipoproteins and recombinant protein was tested using biolayer interferometry. An association between human genetic variants and circulating Lp(a) levels was analyzed in the UK Biobank cohort.

RESULTS

The top positive and negative regulators of Lp(a) uptake in our screen were LDLR and MYLIP, encoding the LDL receptor and its ubiquitin ligase IDOL, respectively. We also found a significant correlation for other genes with established roles in LDLR regulation. No other gene products, including those previously proposed as Lp(a) receptors, exhibited a significant effect on Lp(a) uptake in our screen. We validated the functional influence of LDLR expression on HuH7 Lp(a) uptake, confirmed in vitro binding between the LDLR extracellular domain and purified Lp(a), and detected an association between loss-of-function LDLR variants and increased circulating Lp(a) levels in the UK Biobank cohort.

CONCLUSIONS

Our findings support a central role for the LDL receptor in mediating Lp(a) uptake by hepatocytes.

Lerodalcibep and evolocumab for the treatment of homozygous familial hypercholesterolaemia with PCSK9 inhibition (LIBerate-HoFH): a phase 3, randomised, open-label, crossover, non-inferiority trial

BACKGROUND

Lerodalcibep, a small binding anti-PCSK9 protein (adnectin), showed effective LDL cholesterol reduction in heterozygous familial hypercholesterolaemia. We aimed to assess the safety and efficacy of lerodalcibep and evolocumab in a globally diverse homozygous familial hypercholesterolaemia population.

METHODS

This phase 3, randomised, open-label, crossover, non-inferiority study consisted of two 24-week treatment periods separated by an 8-week washout. The study was conducted in 12 lipid clinics in six countries (India, Israel, Norway, South Africa, Türkiye, and the USA). Patients aged 10 years or older with genetically confirmed homozygous familial hypercholesterolaemia were randomly assigned by computer-generated randomisation scheme performed centrally via interactive response technology to either monthly lerodalcibep 300 mg (1·2 mL subcutaneous injection) or monthly evolocumab 420 mg (subcutaneous 9 min infusion of 3·5 mL) for 24 weeks (period A) followed by an 8-week washout and then crossed over to the alternate therapy for the next 24 weeks (period B). The trial was open label, but all efficacy parameters were masked to patients, study staff, and the sponsor from randomisation. The primary efficacy endpoint was the percent change from baseline (day 1 of period A) in LDL cholesterol concentration to week 24 for period A and B. The intention-to-treat (ITT) population, defined as all randomly assigned patients, was used for the primary analysis. The safety population included all patients who received any study medication. The margin used to establish non-inferiority was 6%. The trial is registered with ClinicalTrials.gov (NCT04034485) and EudraCT (2019-003611-62), and has now finished.

FINDINGS

Patients were enrolled from Nov 11, 2019, to July 2, 2021, and the final study visit took place on Aug 8, 2022. Of 82 patients screened, 66 entered period A (ITT population). The mean age was 28·7 years (SD 15·2); 20 (30%) of 66 were paediatric patients; 36 (55%) of 66 were female and 30 (45%) of 66 were male; and the mean baseline LDL cholesterol was 10·59 mmol/L (SD 4·37). Mean LDL cholesterol reduction by ITT analysis at week 24 was -4·9% (SE 3·5) on lerodalcibep compared with -10·3% (3·5) on evolocumab; the mean difference between treatments was 5·4% (95% CI -0·2 to 11·1), which did not show non-inferiority at the prespecified 6% margin. LDL cholesterol response varied considerably across the patient population but was generally similar in the same patients with both lerodalcibep and evolocumab. When averaged across all monthly visits, LDL cholesterol response was -9·1% (SE 3·2) on lerodalcibep and -10·8% (3·2) on evolocumab. Importantly, genotyping and free PCSK9 suppression were not predictive of response. Both drugs were well tolerated, with no treatment-related serious adverse events. Injection site reactions were reported in one (2%) of 65 patients on lerodalcibep and 15 (24%) of 62 patients on evolocumab.

INTERPRETATION

The LDL cholesterol response was highly variable, but generally similar in patients treated with both lerodalcibep and evolocumab. Importantly, the study showed the inability to predict response based on genotyping, reinforcing the rationale for PCSK9 inhibition in all patients with homozygous familial hypercholesterolemia and continuing its use in responders.

FUNDING

LIB Therapeutics.

Resistance to conventional drug therapy and good response to lomitapide allowed the identification of a novel bi-allelic semi-dominant monogenic HoFH: a case report

INTRODUCTION

Familial hypercholesterolaemia (FH) is a genetic disorder associated with high cholesterol levels and an increased risk of premature cardiovascular events. Rare forms, such as semi-dominant bi-allelic mutations, pose diagnostic and therapeutic challenges. Misdiagnosis of FH is a significant concern, as highlighted by both this case and a review of the literature.

CASE REPORT

We report the case of a 54-year-old woman with an acute myocardial infarction at the age of 43 years. She had a positive family history of early cardiovascular events and was diagnosed with familial hypercholesterolaemia at the age of 33 years. She tried statins with no benefit. In 2017, evolocumab was introduced but was insufficient to control cholesterol values (low-density lipoprotein cholesterol 324 mg/dL). She started lomitapide, and next-generation sequencing screening was performed in consideration of the different pharmacological effects and clinical trends compared to other family members. A bi-allelic semi-dominant mutation (c.241C > T in exon 3 of the LDLR gene) was found in addition to the previously identified mutation. She is now in good clinical condition and laboratory response with lomitapide, evolocumab, statin, and ezetimibe. A literature review was conducted to explore the clinical and diagnostic challenges of FH, with a focus on the risk of misdiagnosis.

CONCLUSION

This case underscores the importance of genetic testing in diagnosing rare forms of FH, such as semi-dominant bi-allelic mutations, which may lead to misdiagnosis. Lomitapide proved effective in controlling cholesterol levels, highlighting its value in managing complex FH cases. The literature review further emphasizes the critical need for improved diagnostic approaches to minimize the risk of misdiagnosis.

Large-Scale Functional Characterization of Low-Density Lipoprotein Receptor Gene Variants Improves Risk Assessment in Cardiovascular Disease

Limited access to functional information of genetic variants reduces the applicability of genetic tools for precision medicine applications in cardiovascular disease. We established an automated analysis platform based on multiplexed high-content imaging and derived in-depth functional data for several hundred LDLR gene variants. Residual low-density lipoprotein receptor activity of genetic variants impacted the risk for cardiovascular disease and elevated low-density lipoprotein cholesterol as well as the utilization of lipid-lowering and combination therapy. This enables increased risk stratification for carriers of LDLR gene variants and opens up new opportunities for improved diagnosis, risk assessment, and treatment selection in familial hypercholesterolemia.

Expanding the clinical spectrum of 19p13.3 microduplication syndrome: a case report highlighting nephrotic syndrome and literature review

BACKGROUND

Common clinical findings in patients with 19p13.3 duplication include intrauterine growth restriction, intellectual disability, developmental delay, microcephaly, and distinctive facial features. In this study, we report the case of a patient with 19p13.3 microduplication and novel clinical findings, specifically nephrotic syndrome.

CASE PRESENTATIONS

A 4-year-old girl was admitted to our hospital in December 2020 with a fever and cough that had persisted for 3 days. A series of treatments, chromosomal microarray analysis (CMA) and whole exome sequencing (WES) were performed. Relevant literature was reviewed using the search terms "19p13.3" and "19p13.3 microduplication syndrome" in the China Knowledge Network, Wanfang Database, Weipu Journal Service Platform, and PubMed (date range: database establishment to September 2023). In addition to common symptoms, such as developmental delay, microcephaly, distinctive facial features, and congenital heart defects, the patient also had nephrotic syndrome, a previously unreported phenomenon. CMA results showed a 3.6 Mb fragment duplication (copy number: 3) in the chr19p13.3 region, containing 127 protein-coding genes (including CELF5, NFIC, SMIM24, PIAS4, ATCAY, MAP2K2, and ZBTB7A). WES revealed a filamin C mutation (p.Glu309Valfs × 11). The mutation status of the patient and her father was heterozygous, whereas the mutation was not detected in the mother.

CONCLUSION

Microduplication in the 19p13.3 region could be one of the genetic factors contributing to the observed clinical phenotypes. However, patients with developmental delay, microcephaly, distinctive facial features, congenital heart defects, and urogenital system disorders may exhibit these manifestations due to various genetic syndromes; therefore, simply considering the possibility of 19p13.3 microduplication syndrome based on these non-specific features is not sufficient. Further comprehensive evaluations, including CMA, should be conducted in conjunction with other genetic tests and detailed clinical examinations to accurately determine the underlying genetic causes.

Pathogenicity assessment of genetic variants identified in patients with severe hypertriglyceridemia: Novel cases of familial chylomicronemia syndrome from the Dyslipidemia Registry of the Spanish Atherosclerosis Society

PURPOSE

Genetic testing is required to confirm a diagnosis of familial chylomicronemia syndrome (FCS). We assessed the pathogenicity of variants identified in the FCS canonical genes to diagnose FCS cases.

METHODS

245 patients with severe hypertriglyceridemia underwent next-generation sequencing. Preliminary variant pathogenicity criteria and classification, based on the American College of Medical Genetics and Genomics guidelines, were obtained online and verified. Phenotype evaluation was based on lipoprotein lipase activity deficiency, a clinical score, and/or type I hyperlipoproteinemia determined in 25 patients.

RESULTS

Twenty-four biallelic variants were analyzed. Evidence-based criteria allowed the reclassification of 8 likely pathogenic (LP) variants in the LPL, APOA5, and LMF1 genes into pathogenic (P) and the change of 2 variants of uncertain significance (VUS) to LP. Conversely, 2 variations in LMF1 remained as VUS. Additionally, 1 variant in LPL and 2 in GPIHBP1 were likely benign. Twenty FCS cases had biallelic P/LP variants and 1 patient, with an FCS phenotype, harbored biallelic VUS. FCS was excluded from 4 patients with pathogenic/likely benign combinations.

CONCLUSION

The analysis of the clinical and biochemical features of patients with variants in the FCS canonical genes allowed a confident variant classification that helped in the diagnosis of novel FCS cases.

Familial hypercholesterolemia in Chinese children and adolescents: a multicenter study

BACKGROUND

Familial hypercholesterolemia (FH) is an inherited disorder mainly marked by increased low-density lipoprotein cholesterol (LDL-C) concentrations and a heightened risk of early-onset arteriosclerotic cardiovascular disease (ASCVD). This study seeks to characterize the genetic spectrum and genotype‒phenotype correlations of FH in Chinese pediatric individuals.

METHODS

Data were gathered from individuals diagnosed with FH either clinically or genetically at multiple hospitals across mainland China from January 2016 to June 2024.

RESULTS

In total, 140 children and adolescents (mean age of 6.00 years) with clinically and genetically diagnosed FH were enrolled in the study, with 87 distinct variants identified in the LDLR, APOB and PCSK9 genes. Among the variants, 11 variants were newly identified worldwide, with 9 classified as "pathogenic" or "likely pathogenic", and 2 classified as "variants of uncertain significance". Additionally, the 5 most common variants in the study were c.1448G > A (p.W483*), c.1879G > A (p.A627T), c.1216C > A (p.R406R), and c.1747C > T (p.H583Y) in the LDLR gene, as well as c.10579C > T (p.R3527W) in the APOB gene, accounting for 49.29% (69/140) of all patients. These variants are primarily observed in the Asian or Chinese population and are distinct from those present in Caucasian groups. In this cohort, 105 patients were diagnosed with heterozygous FH (HeFH), while 35 were diagnosed with homozygous FH (HoFH). Finally, only 28.57% of the patients (40/140) were using lipid-lowering medications with 33.33% of HoFH patients initiating treatment after the age of 8. Additionally, only 3 compound heterozygous patients (2.14%) underwent liver transplantation because of significantly high lipid levels.

CONCLUSION

This study reveals the variable genotypes and phenotypes of children with FH in China and illustrates that the genotypes in the Chinese population differ from those in Caucasians, providing a valuable dataset for the clinical genetic screening of FH in China. Furthermore, the older age at diagnosis and treatment highlights the underdiagnosis and undertreatment of Chinese FH pediatric patients, suggesting that early identification should be improved through lipid or genetic screening, and that more timely and regular pharmacological treatments should be implemented.

Clinical and biochemical features of atherogenic hyperlipidemias with different genetic basis: A comprehensive comparative study

Patients with genetically-based hyperlipidemias exhibit a wide phenotypic variability. Investigation of clinical and biochemical features is important for identifying genetically-based hyperlipidemias, determining disease prognosis, and initiating timely treatment. We analyzed genetic data from 3374 samples and compared clinical data, lipid levels (low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, triglycerides, and lipoprotein (a)), frequency, age at onset of coronary heart disease (CHD), and the severity of carotid and femoral atherosclerosis (plaque number, maximum stenosis, total stenosis, maximum plaque height, and plaque score) among patients with familial hypercholesterolemia (FH), familial dysbetalipoproteinemia (FD), polygenic hypercholesterolemia (HCL), severe HCL, and those without lipid disorders (n = 324). FH patients exhibited the highest LDL-C (median 8.03 mmol/L, p < 0.001). FD patients had elevated triglyceride levels (median 4.10 mmol/L), lower LDL-C (median 3.57 mmol/L), and high-density lipoprotein cholesterol (median 1.03 mmol/L) compared to FH, polygenic HCL, and severe HCL, p < 0.05. FH and FD patients had similar early onset of CHD, with a median age of 44 and 40 years and comparable frequencies of 29.5% and 31.0%, respectively. They were more likely to develop CHD than subjects without lipid disorders (p = 0.042 and p < 0.001, respectively). Additionally, FH patients had higher a carotid plaque number, total carotid stenosis, and carotid plaque score. This study presents the first simultaneous comparison of clinical and biochemical features among FD, FH, polygenic, and severe HCL, along with the first comprehensive evaluation of carotid and femoral atherosclerosis ultrasound parameters in FD patients. The results highlight distinct phenotypic features unique to each hyperlipidemia analyzed and underscore FH and FD as the most atherogenic hyperlipidemias.

Improved Genetic Characterization of Hypercholesterolemia in Latvian Patients with Familial Hypercholesterolemia: A Combined Monogenic and Polygenic Approach Using Whole-Genome Sequencing

Despite the implementation of next-generation sequencing-based genetic testing on patients with clinical familial hypercholesterolemia (FH), most cases lack complete genetic characterization. We aim to investigate the utility of the polygenic risk score (PRS) in specifying the genetic background of patients from the Latvian Registry of FH (LRFH). We analyzed the whole-genome sequencing (WGS) data of the clinically diagnosed FH patients (n = 339) and controls selected from the Latvian reference population (n = 515). Variant pathogenicity in FH patients was classified according to the ACMG/AMP guidelines. The low-density lipoprotein cholesterol (LDL-C) and lipoprotein (a) (LPA) PRS were calculated based on the WGS data. We identified unique causative variants in 80 (23.6%) of the tested individuals (39 variants in FH genes and 4 variants in phenocopy genes, with 6 variants being novel). The LDL-C PRS was highly discriminative compared to the LPA PRS. Nevertheless, both PRS were able to explain the genetic cause of hypercholesterolemia in 26.3% of the remaining non-monogenic patients. The combined genetic analysis of monogenic and polygenic hypercholesterolemia resulted in 43.7% genetically explained hypercholesterolemia cases. Even though the application of PRS alone does not exclude monogenic testing in clinical FH patients, it is a valuable tool for diagnosis specification.

Universal screening for familial hypercholesterolaemia: how can we maximise benefits and minimise potential harm for children and their families?

PURPOSE OF REVIEW

Universal Screening programmes to identify subjects with familial hypercholesterolaemia (FH) have been the subject of much recent interest. However, any screening programme can cause harm as well as having potential benefits. Here we review recent papers using different ages and strategies to identify subjects with FH, and examine to what extent the publications provide quantitative or qualitative evidence of benefit or harm to children and adults.

RECENT FINDINGS

Three studies have been published over the last 2 years where Universal Screening for FH has been carried out in infancy, at the time of routine vaccinations, or at preschool age. Next-generation sequencing of all known FH-causing genes has been used to determine the proportion of screened individuals, who have total or low-density lipoprotein cholesterol (LDL-C) concentrations above a predetermined threshold (such as >95th percentile), with genetically confirmed FH.

SUMMARY

While we fully support the concept of Universal Screening for FH, which appears feasible and of potential clinical utility at all of the different ages examined, there is little data to document potential benefit or how to mitigate potential harms. Future study protocols should include collection of such data to strengthen the case of roll out of Universal Screening programmes.

Canadian College of Medical Geneticists: clinical practice advisory document - responsibility to recontact for reinterpretation of clinical genetic testing

BACKGROUND

Advances in technology and knowledge have facilitated both an increase in the number of patient variants reported and variants reclassified. While there is currently no duty to recontact for reclassified genetic variants, there may be a responsibility. The purpose of this clinical practice advisory document is to provide healthcare practitioners guidance for recontact of previously identified and classified variants, suggest methods for recontact, and principles to consider, taking account patient safety, feasibility, ethical considerations, health service capacity and resource constraints. The target audience are practitioners who order genetic testing, follow patients who have undergone genetic testing and those analysing and reporting genetic testing.

METHODS

A multidisciplinary group of laboratory and ordering clinicians, patient representatives, ethics and legal researchers and a genetic counsellor from the Canadian Association of Genetic Counsellors reviewed the existing literature and guidelines on responsibility to recontact in a clinical context to make recommendations. Comments were collected from the Canadian College of Medical Geneticists (CCMG) Education, Ethics, and Public Policy, Clinical Practice and Laboratory Practice committees, and the membership at large.

RESULTS

Following incorporation of feedback, and external review by the Canadian Association of Genetic Counsellors and patient groups, the document was approved by the CCMG Board of Directors. The CCMG is the Canadian organisation responsible for certifying laboratory and medical geneticists who provide medical genetics services, and for establishing professional and ethical standards for clinical genetics services in Canada.

CONCLUSION

The document describes the ethical and practical factors and suggests a shared responsibility between patients, ordering clinician and laboratory practitioners.

Portuguese Lipid Study (e_LIPID)

Background/Objectives: Incidence of cardiovascular disease (CVD) is increasing in low- and middle-income countries because of changing lifestyles. Since dyslipidaemia is a major independent cardiovascular risk factor, its correct identification is critical to implement specific interventions for CVD prevention. This study aimed to characterise the lipid profile of the Portuguese population. Methods: Overall, 1688 individuals from the general population (e_COR study, 2012-2014) were included. Population-specific percentiles for ten lipid biomarkers were estimated by bootstrapping methods to ensure national representativity. Statistical analyses were performed using RStudio. Results: The 50th percentile estimated for total cholesterol (TC), LDL-C, and non-HDL-C are similar to scientific societies recommended values for the general (low or moderate risk) population. National prevalence of having lipid parameters above recommended values was 64.6%, 66.9%, 51.3%, 68.9%, 17.8%, and 21.1% for TC, LDL-C, apoB, non-HDL-C, triglycerides, and Lp(a), respectively; these values are generally higher in men and increasing with age, except for Lp(a). A high prevalence of severe dyslipidaemia (>90th percentile) was identified, highest for small dense LDL-C (31.3%), apoB (30.4%), and LDL-C (30.3%). The national prevalence of CVD events was 5%. Three individuals were genetically identified with familial hypercholesterolemia, a high CVD risk condition. Conclusions: We provide for the first-time lipid biomarker percentiles for the general Portuguese population. Our results highlight that hypercholesterolemia is a neglected cardiovascular risk factor with over half of the population with TC, LDL-C, and apoB above recommended values. Since hypercholesterolemia is a modifiable risk factor, strategies to increase adherence to changes in lifestyle habits and medication need to be urgently discussed.

A Rapid and Scalable Multiplex PCR-Based Next-Generation Amplicon Sequencing Method for Familial Hypercholesterolemia Genetic Screening

BACKGROUND

Familial hypercholesterolemia (FH) is a frequently underdiagnosed genetic disorder characterized by elevated low-density lipoprotein (LDL) levels. Genetic testing of LDLR, APOB, and PCSK9 genes can identify variants in up to 80% of clinically diagnosed patients. However, limitations in time, scalability, and cost have hindered effective next-generation sequencing of these genes. Additionally, pharmacogenomic variants are associated with statin-induced adverse effects in FH patients. To address these challenges, we developed a multiplex primer-based amplicon sequencing approach for FH genetic testing.

METHODS

Multiplex primers were designed for the exons of the LDLR, APOB, and PCSK9 genes, as well as for pharmacogenomic variants rs4149056 (SLCO1B1:c.521T > A), rs2306283 (SLCO1B1:c.388A > G), and rs2231142 (ABCG2:c.421C > A). Analytical validation using samples with known pathogenic variants and clinical validation with 12 FH-suspected probands were conducted. Library preparation was based on a bead-based tagmentation method, and sequencing was conducted on the NovaSeq 6000 platform.

RESULTS

Our approach ensured no amplicon dropouts, with over 100× coverage on each amplicon. Known variants in 2 samples were successfully detected. Further, we identified one heterozygous LDLR (p.Glu228Ter) variant and 2 homozygous cases of LDLR (p.Lys294Ter) and LDLR (p.Ser177Leu) variants in patients. Pharmacogenomic analysis revealed that overall 3 patients may require reduced statin doses. Our approach offered reduced library preparation time (approximately 3 h), greater scalability, and lower costs (under $50) for FH genetic testing.

CONCLUSIONS

Our method effectively sequences LDLR, APOB, and PCSK9 genes including pharmacogenomic variants that will guide appropriate screening and statin dosing, thus increasing both efficiency and affordability.

Challenges and opportunities for identifying people with familial hypercholesterolemia in the UK: Evidence from the National FH PASS database

BACKGROUND

Familial hypercholesterolemia (FH) is a monogenic disorder that causes high levels of low-density lipoprotein (LDL) cholesterol. Cascade testing, where relatives of known individuals with FH ('index') are genetically tested, is effective and cost-effective, but implementation in the UK varies.

OBJECTIVE

This study aims to provide evidence on current UK FH cascade yields and to identify common obstacles cascade services face and individual- and service-level predictors of success.

METHODS

Electronic health records from 875 index families and 5,958 linked relatives in the UK's Welsh and Wessex FH services (2019) were used to explore causes for non-testing and to estimate testing rates, detection yields, and how relative characteristics and contact methods relate to the probability of relatives being tested (using logistic regression).

RESULTS

In Wales (Wessex), families included 7.35 (7.01) members on average, with 2.41 (1.66) relatives tested and 1.35 (0.96) diagnosed with FH per index. Cascade testing is limited by individualized circumstances (too young, not at-risk, etc.) and FH services' reach, with approximately one in four relatives out-of-area. In Wales, first-degree relatives (odds ratio (OR): 1.55 [95% confidence interval (CI): 1.28, 1.88]) and directly contacted relatives (OR: 2.11 [CI: 1.66, 2.69]) were more likely to be tested. In Wales and Wessex, women were more likely to be tested than men (ORs: 1.53 [CI: 1.28, 1.85] and 1.74 [CI: 1.32, 2.27]).

CONCLUSION

In Wales and Wessex less than a third of relatives of an index are tested for FH. Improvements are likely possible by integrating geographically dispersed families into cascade testing, services directly contacting relatives where possible, and finding new ways to encourage participation, particularly amongst men.

Enhancing Familial Hypercholesterolemia Detection in South Korea: A Targeted Screening Approach Integrating National Program and Genetic Cascade Screening

BACKGROUND AND OBJECTIVES

Familial hypercholesterolemia (FH) increases the risk of premature cardiovascular disease through disrupted low-density lipoprotein cholesterol (LDL-C) metabolism. Although FH is a severe condition, it remains widely underdiagnosed, which can be attributed to barriers in genetic testing and a lack of awareness. This study aims to propose and evaluate a targeted screening program for FH in South Korea by integrating the General Health Screening Program (GHSP) with cascade genetic screening.

METHODS

The study included individuals with LDL-C levels ≥190 mg/dL identified during the 2021 GHSP (primary participants). Data on demographics, lifestyle, medical history, and family history were collected through questionnaires. Targeted next-generation sequencing was used to identify pathogenic mutations in the PCSK9, APOB, LDLRAP1, and LDLR genes associated with FH. Pathogenic mutations found in primary participants were confirmed in their relatives (secondary participants) using Sanger sequencing. Participant characteristics were analyzed based on the presence of pathogenic mutations.

RESULTS

Among 83 individuals with severe hypercholesterolemia identified through the GHSP, 7 primary participants (8.4%) carried pathogenic mutations in the LDLR and PCSK9 genes. In secondary participants, pathogenic mutations were identified in 61.1% of the relatives of 4 patients with pathogenic mutations. The prevalence of pathogenic mutations was significantly higher in primary participants compared to secondary participants.

CONCLUSIONS

Integrating community resources with FH screening can enhance the early detection and treatment of FH. By utilizing GHSP data and adding genetic screening, the proposed model provides a strategy to reduce the cardiovascular risks associated with FH, supporting its wider adoption at the national level.

Analysis of low-density lipoprotein receptor gene mutations in a family with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is a common monogenic autosomal dominant disorder, primarily mainly caused by pathogenic mutations in the low-density lipoprotein receptor (LDLR) gene. Through phenotypic-genetic linkage analysis, two LDLR pathogenic mutations were identified in FH families: c.G1027A (p.Gly343Ser) and c.G1879A (p.Ala627Thr).

MATERIALS AND METHODS

Whole exome sequencing was conducted on the proband with familial hypercholesterolemia to identify the target gene and screen for potential pathogenic mutations. The suspicious responsible mutation sites in 14 family members were analyzed using Sanger sequencing to assess genotype-phenotype correlations. Mutant and wild type plasmids were constructed and transfected into HEK293T cells to evaluate LDLR mRNA and protein expression. In parallel, bioinformatics tools were employed to predict structural and functional changes in the mutant LDLR.

RESULTS

Immunofluorescence analysis revealed no significant difference in the intracellular localization of the p.Gly343Ser mutation, whereas protein expression of the p.Ala627Thr mutation was decreased and predominantly localized in the cytoplasm. Western blotting has showed that protein expression levels of the mutant variants were markedly declined in both cell lysates and supernatants. Enzyme linked immunosorbent assay has demonstrated that LDLR protein levels in the supernatant of cell culture medium was not significant different from those of the wild-type group. However, LDLR protein levels in the cell lysate of both the Gly343Ser and Ala627Thr variants groups were significantly lower than those in the wild-type group. Bioinformatic predictions further suggested that these mutations may affect post-translational modifications of the protein, providing additional insight into the mechanisms underlying the observed reduction in protein expression.

CONCLUSIONS

In this study, we identified two heterozygous pathogenic variants in the LDLR gene, c.G1027A (p.Gly343Ser) and c.G1879A (p.Ala627Thr), in a family with familial hypercholesterolemia. We also conducted preliminary investigations into the mechanisms by which these mutations contribute to disease pathology.

Potentials of artificial intelligence in familial hypercholesterolemia: Advances in screening, diagnosis, and risk stratification for early intervention and treatment

Familial hypercholesterolemia (FH) poses a global health challenge due to high incidence rates and underdiagnosis, leading to increased risks of early-onset atherosclerosis and cardiovascular diseases. Early detection and treatment of FH is critical in reducing the risk of cardiovascular events and improving the long-term outcomes and quality of life for affected individuals and their families. Traditional therapeutic approaches revolve around lipid-lowering interventions, yet challenges persist, particularly in accurate and timely diagnosis. The current diagnostic landscape heavily relies on genetic testing of specific LDL-C metabolism genes, often limited to specialized centers. This constraint has led to the adoption of alternative clinical scores for FH diagnosis. However, the rapid advancements in artificial intelligence (AI) and machine learning (ML) present promising solutions to these diagnostic challenges. This review explores the intricacies of FH, highlighting the challenges that are encountered in the diagnosis and management of the disorder. The revolutionary potential of ML, particularly in large-scale population screening, is highlighted. Applications of ML in FH screening, diagnosis, and risk stratification are discussed, showcasing its ability to outperform traditional criteria. However, challenges and ethical considerations, including algorithmic stability, data quality, privacy, and consent issues, are crucial areas that require attention. The review concludes by emphasizing the significant promise of AI and ML in FH management while underscoring the need for ethical and practical vigilance to ensure responsible and effective integration into healthcare practices.

Calibration of variant effect predictors on genome-wide data masks heterogeneous performance across genes

In silico variant effect predictions are available for nearly all missense variants but played a minimal role in clinical variant classification because they were deemed to provide only supporting evidence. Recently, the ClinGen Sequence Variant Interpretation (SVI) Working Group updated recommendations for variant effect prediction use. By analyzing control pathogenic and benign variants across all genes, they were able to compute evidence strength for predictor score intervals with some intervals generating moderate, strong, or even very strong evidence. However, this genome-wide approach could obscure heterogeneous predictor performance in different genes. We quantified the gene-by-gene performance of two top predictors, REVEL and BayesDel, by analyzing control variants in each predictor score interval in 3,668 disease-relevant genes. Approximately 10% of intervals had sufficient control variants for analysis, and ∼70% of these intervals exceeded the maximum number of incorrect predictions implied by the SVI recommendations. These trending discordant intervals arose owing to the divergence of the gene-specific distribution of predictions from the genome-wide distribution, suggesting that gene-specific calibration is needed in many cases. Approximately 22% of ClinVar missense variants of uncertain significance in genes we analyzed (REVEL = 100,629, BayesDel = 71,928) had predictions in trending discordant intervals. Thus, genome-wide calibrations could result in many variants receiving inappropriate evidence strength. To facilitate a review of the SVI's calibrations, we developed a web application enabling visualization of gene-specific predictions and trending concordant and discordant intervals.

Consensus document on diagnosis and management of familial hypercholesterolemia from the Italian Society for the Study of Atherosclerosis (SISA)

AIMS

Familial Hypercholesterolemia (FH) is a genetic disorder of lipoprotein metabolism that causes an increased risk of premature atherosclerotic cardiovascular disease (ASCVD). Although early diagnosis and treatment of FH can significantly improve the cardiovascular prognosis, this disorder is underdiagnosed and undertreated. For these reasons the Italian Society for the Study of Atherosclerosis (SISA) assembled a Consensus Panel with the task to provide guidelines for FH diagnosis and treatment.

DATA SYNTHESIS

Our guidelines include: i) an overview of the genetic complexity of FH and the role of candidate genes involved in LDL metabolism; ii) the prevalence of FH in the population; iii) the clinical criteria adopted for the diagnosis of FH; iv) the screening for ASCVD and the role of cardiovascular imaging techniques; v) the role of molecular diagnosis in establishing the genetic bases of the disorder; vi) the current therapeutic options in both heterozygous and homozygous FH. Treatment strategies and targets are currently based on low-density lipoprotein cholesterol (LDL-C) levels, as the prognosis of FH largely depends on the magnitude of LDL-C reduction achieved by lipid-lowering therapies. Statins with or without ezetimibe are the mainstay of treatment. Addition of novel medications like PCSK9 inhibitors, ANGPTL3 inhibitors or lomitapide in homozygous FH results in a further reduction of LDL-C levels. LDL apheresis is indicated in FH patients with inadequate response to cholesterol-lowering therapies.

CONCLUSION

FH is a common, treatable genetic disorder and, although our understanding of this disease has improved, many challenges still remain with regard to its identification and management.

Variant classification changes over time in the clinical molecular diagnostic laboratory setting

BACKGROUND

Variant classification in the setting of germline genetic testing is necessary for patients and their families to receive proper care. Variants are classified as pathogenic (P), likely pathogenic (LP), uncertain significance (VUS), likely benign (LB) and benign (B) using the standards and guidelines recommended by the American College of Medical Genetics and the Association for Molecular Pathology, with modifications for specific genes. As the literature continues to rapidly expand, and evidence continues to accumulate, prior classifications can be updated accordingly. In this study, we aim to characterise variant reclassifications in Ontario.

METHODS

DNA samples from patients seen at hereditary cancer clinics in Ontario from January 2012 to April 2022 were submitted for testing. Patients met provincial eligibility criteria for testing for hereditary cancer syndromes or polycystic kidney disease. Reclassification events were determined to be within their broader category of significance (B to LB or vice versa, or P to LP or vice versa) or outside of their broader category as significance (ie, significant reclassifications from B/LB or VUS or P/LP, from P/LP to VUS or B/LB, or from VUS to any other category).

RESULTS

Of the 8075 unique variants included in this study, 23.7% (1912) of variants were reassessed, and 7.2% (578) of variants were reclassified. Of these, 351 (60.7%) variants were reclassified outside of their broader category of significance. Overall, the final classification was significantly different for 336 (58.1%) variants. Importantly, most reclassified variants were downgraded to a more benign classification (n=245; 72.9%). Of note, most reclassified VUS was downgraded to B/LB (n=233; 84.7%).

CONCLUSIONS

The likelihood for reclassification of variants on reassessment is high. Most reclassified variants were downgraded to a more benign classification. Our findings highlight the importance of periodic variant reassessment to ensure timely and appropriate care for patients and their families.

Influence of Polygenic Background on the Clinical Presentation of Familial Hypercholesterolemia

BACKGROUND

Heterozygous familial hypercholesterolemia (FH) is among the most common genetic conditions worldwide that affects ≈ 1 in 300 individuals. FH is characterized by increased levels of low-density lipoprotein cholesterol (LDL-C) and increased risk of coronary artery disease (CAD), but there is a wide spectrum of severity within the FH population. This variability in expression is incompletely explained by known risk factors. We hypothesized that genome-wide genetic influences, as represented by polygenic risk scores (PRSs) for cardiometabolic traits, would influence the phenotypic severity of FH.

METHODS

We studied individuals with clinically diagnosed FH (n=1123) from the FH Canada National Registry, as well as individuals with genetically identified FH from the UK Biobank (n=723). For all individuals, we used genome-wide gene array data to calculate PRSs for CAD, LDL-C, lipoprotein(a), and other cardiometabolic traits. We compared the distribution of PRSs in individuals with clinically diagnosed FH, genetically diagnosed FH, and non-FH controls and examined the association of the PRSs with the risk of atherosclerotic cardiovascular disease.

RESULTS

Individuals with clinically diagnosed FH had higher levels of LDL-C, and the incidence of atherosclerotic cardiovascular disease was higher in individuals with clinically diagnosed compared with genetically identified FH. Individuals with clinically diagnosed FH displayed enrichment for higher PRSs for CAD, LDL-C, and lipoprotein(a) but not for other cardiometabolic risk factors. The CAD PRS was associated with a risk of atherosclerotic cardiovascular disease among individuals with an FH-causing genetic variant.

CONCLUSIONS

Genetic background, as expressed by genome-wide PRSs for CAD, LDL-C, and lipoprotein(a), influences the phenotypic severity of FH, expanding our understanding of the determinants that contribute to the variable expressivity of FH. A PRS for CAD may aid in risk prediction among individuals with FH.

Improving the Detection of Potential Cases of Familial Hypercholesterolemia: Could Machine Learning Be Part of the Solution?

BACKGROUND

Familial hypercholesterolemia (FH), while highly prevalent, is a significantly underdiagnosed monogenic disorder. Improved detection could reduce the large number of cardiovascular events attributable to poor case finding. We aimed to assess whether machine learning algorithms outperform clinical diagnostic criteria (signs, history, and biomarkers) and the recommended screening criteria in the United Kingdom in identifying individuals with FH-causing variants, presenting a scalable screening criteria for general populations.

METHODS AND RESULTS

Analysis included UK Biobank participants with whole exome sequencing, classifying them as having FH when (likely) pathogenic variants were detected in their LDLR, APOB, or PCSK9 genes. Data were stratified into 3 data sets for (1) feature importance analysis; (2) deriving state-of-the-art statistical and machine learning models; (3) evaluating models' predictive performance against clinical diagnostic and screening criteria: Dutch Lipid Clinic Network, Simon Broome, Make Early Diagnosis to Prevent Early Death, and Familial Case Ascertainment Tool. One thousand and three of 454 710 participants were classified as having FH. A Stacking Ensemble model yielded the best predictive performance (sensitivity, 74.93%; precision, 0.61%; accuracy, 72.80%, area under the receiver operating characteristic curve, 79.12%) and outperformed clinical diagnostic criteria and the recommended screening criteria in identifying FH variant carriers within the validation data set (figures for Familial Case Ascertainment Tool, the best baseline model, were 69.55%, 0.44%, 65.43%, and 71.12%, respectively). Our model decreased the number needed to screen compared with the Familial Case Ascertainment Tool (164 versus 227).

CONCLUSIONS

Our machine learning-derived model provides a higher pretest probability of identifying individuals with a molecular diagnosis of FH compared with current approaches. This provides a promising, cost-effective scalable tool for implementation into electronic health records to prioritize potential FH cases for genetic confirmation.

LDLR c.89_92dup: a novel frameshift variation in familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is a common inherited metabolic disease that causes premature atherosclerosis, cardiovascular disease, and even death at a young age. Approximately 95% of FH-causing genetic variants that have been identified are in the LDLR gene. However, only 10% of the FH population worldwide has been diagnosed and adequately treated, due to the existence of numerous unidentified variants, uncertainties in the pathogenicity scoring of many variants, and a substantial number of individuals lacking access to genetic testing.

OBJECTIVE

The aim of this study was to identify a novel variant in the LDLR gene that causes FH in a Chinese family, thereby expanding the spectrum of FH-causing variants.

METHODS

Patients were recruited from Beijing Anzhen Hospital, Capital Medical University. FH diagnosis was made according to the Dutch Lipid Clinical Network (DLCN) criteria. Whole-exome sequencing (WES) was conducted to identify the FH-causing variant in the proband, and amplicon sequencing was used to verify the variant in his family members.

RESULTS

A three-generation Chinese family was recruited, and two FH patients were clinically diagnosed, both without known FH-causing variants. These two FH patients and another possible patient carried a novel variant, NC_000019.9(NM_000527.5):c.89_92dup (NP_000518.1:p.Phe32Argfs*21), in the ligand-binding domain of the low-density lipoprotein (LDL) receptor that led to a frameshift. The FH adults in the family showed severe clinical symptoms and statin therapy resistance.

CONCLUSION

This study identified a novel pathogenic LDLR variant, c.89_92dup, associated with severe FH clinical manifestations and statin therapy resistance.

Functional interrogation of cellular Lp(a) uptake by genome-scale CRISPR screening

An elevated level of lipoprotein(a), or Lp(a), in the bloodstream has been causally linked to the development of atherosclerotic cardiovascular disease and calcific aortic valve stenosis. Steady state levels of circulating lipoproteins are modulated by their rate of clearance, but the identity of the Lp(a) uptake receptor(s) has been controversial. In this study, we performed a genome-scale CRISPR screen to functionally interrogate all potential Lp(a) uptake regulators in HuH7 cells. Strikingly, the top positive and negative regulators of Lp(a) uptake in our screen were LDLR and MYLIP, encoding the LDL receptor and its ubiquitin ligase IDOL, respectively. We also found a significant correlation for other genes with established roles in LDLR regulation. No other gene products, including those previously proposed as Lp(a) receptors, exhibited a significant effect on Lp(a) uptake in our screen. We validated the functional influence of LDLR expression on HuH7 Lp(a) uptake, confirmed in vitro binding between the LDLR extracellular domain and purified Lp(a), and detected an association between loss-of-function LDLR variants and increased circulating Lp(a) levels in the UK Biobank cohort. Together, our findings support a central role for the LDL receptor in mediating Lp(a) uptake by hepatocytes.

Two Cases of Sitosterolemia Falsely Diagnosed as Familial Hypercholesterolemia: Could Digging Deeper Have Avoided Harm?

Sitosterolemia is a rare monogenic lipid disease characterized by the excessive uptake of phytosterols and their accumulation in blood and tissues. Clinically, it can present with hypercholesterolemia and xanthomas, often causing it to be misdiagnosed as familial hypercholesterolemia (FH). The diagnosis of sitosterolemia can easily be confirmed and distinguished from FH with a sterol profile and genetic investigations. Here, we report a sibship of 2 sisters with sitosterolemia initially misdiagnosed as FH. This case report illustrates the importance of considering rare conditions, such as sitosterolemia, as a differential diagnosis in patients with hypercholesterolemia, xanthomas, and hematologic anomalies. It also emphasizes the underdiagnosis of sitosterolemia and the benefits of using sterol profiles and genetic testing in the diagnostic process to initiate the appropriate therapy and avoid harm to patients.

Genetic heterogeneity of familial hypercholesterolaemia in two populations from two different countries

BACKGROUND

Familial hypercholesterolemia (FH) is a genetically determined monogenic disorder of predominantly autosomal dominant inheritance. A number of studies on differences in the genetic profile of patients with FH have demonstrated the importance of a more substantive evaluation of genetic features. The aim of this study was to evaluate the genetic profile of patients with clinical FH among Italian and Russian patients.

METHODS

We included 144 Italian and 79 Russian FH patients; clinical diagnosis was based on the same criteria. Patients were divided in: positive to genetic test (one causative variant), inconclusive (only variants of uncertain clinical significance [VUS]), and negative (with likely benign/benign variants, heterozygous variants in LDLRAP1 gene, or without causative variants).

RESULTS

The genetic test was positive in 76.4 % of the Italian patients and in 49.4 % of the Russian patients. The presence of VUS alone was detected in 7.6 % and in 19.0 % (p < 0.001), respectively. Among patients with positive genetic diagnosis, pre-treatment LDL-C levels were higher in the Russian cohort (353.5 ± 111.3 vs. 302.7 ± 52.1 mg/dL, p = 0.009), as well as the percentage of treated patients (53.8 % vs. 14.5 %, p < 0.001) and the prevalence of premature coronary heart disease (12.8 % vs. 3.6 %, p = 0.039). Among patients carrying only VUS, mean pre-treatment LDL-C levels were similar between the cohorts (299.5 ± 68.1 vs. 295.3 ± 46.8 mg/dL, p = 0.863). Among pathogenic/likely pathogenic variants and VUS, only 5 % and 4 % was shared between the two cohorts, respectively.

CONCLUSION

The genetic background of patients clinically diagnosed with FH in two different countries is characterized by high variability.

Evolocumab Treatment in Pediatric Patients With Homozygous Familial Hypercholesterolemia: Pooled Data From Three Open-Label Studies

BACKGROUND

Pediatric patients with homozygous familial hypercholesterolemia (HoFH) have an increased risk of atherosclerotic cardiovascular disease and difficulty meeting low-density lipoprotein cholesterol (LDL-C) goals. In this post hoc analysis, we evaluated pooled safety and efficacy data from 3 studies in pediatric patients with HoFH treated with the PCSK9 (proprotein convertase subtilisin/kexin type 9) monoclonal antibody inhibitor evolocumab.

METHODS

Patients with HoFH aged 10 to 17 years received treatment with open-label evolocumab 420 mg subcutaneously monthly or biweekly in the TAUSSIG, RAMAN, or HAUSER-OLE clinical studies. All patients received background statins with or without ezetimibe. Study duration ranged from 12 to 260 weeks. The primary end point was treatment-emergent adverse events per 100 patient-years. Efficacy end points were changes from baseline to week 12 in lipids and PCSK9.

RESULTS

Of the 39 patients in the pooled analysis, 69.2% were males, median age was 13.0 years, and 79.5% (31/39) had genotyped HoFH with LDLR pathogenic variants. Overall, median exposure to evolocumab was 18.2 (Q1, Q3: 3.0, 18.5) months. Treatment-emergent adverse events with an exposure-adjusted patient incidence rate of ≥5% were upper respiratory tract infection (6.6%), influenza (5.2%), and acne (5.0%) per 100 patient-years. Exposure-adjusted patient incidence of serious treatment-emergent adverse events was 13.3% per 100 patient-years. Excluding 4 patients receiving lipoprotein apheresis, week 12 median percentage change from baseline in LDL-C was -2.9% (Q1, Q3: -21.7, 1.5); however, 42.9% (15/35) of patients achieved ≥15% reduction in LDL-C from baseline. Residual LDLR (LDL receptor) activity was not associated with a reduction in LDL-C.

CONCLUSIONS

In this pooled data analysis from 3 studies in pediatric patients with HoFH, evolocumab was well tolerated, with no new safety signals reported. These safety findings are consistent with findings from previous studies of evolocumab. Patients showed marked variability in LDL-C reduction. Results from this pooled analysis support guidelines suggesting a trial of PCSK9 inhibitor therapy regardless of estimated residual LDLR function.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT01624142, NCT03403374, and NCT02624869.

Simplified Criteria for Identification of Familial Hypercholesterolemia in Children: Application in Real Life

BACKGROUND

The diagnosis of familial hypercholesterolemia (FH) in children is primarily based on main criteria including low-density lipoprotein cholesterol (LDL-C) levels, increased in the proband and relatives, and its inheritance. Two other relevant parameters are symptoms, rarely occurring in children, as rare are the FH homozygous patients, and the mutation detection of related genes. The latter allows the final diagnosis, although it is not commonly available. Moreover, the application of diagnostic scores, useful in adults, is poorly applied in children. The aim of this study was to compare the reliability of criteria here applied with different scores, apart from genetic analysis, for FH diagnosis. The latter was then confirmed by genetic analysis.

METHODS

n. 180 hypercholesterolemic children (age 10.2 ± 4.6 years) showing LDL-C levels ≥95th percentile (age- and sex-related), the dominant inheritance pattern of hypercholesterolemia (including LDL-C ≥95th percentile in one parent), were considered potentially affected by FH and included in the study. The molecular analysis of the LDLR, APOB and PCSK9 genes was applied to verify the diagnostic accuracy. Biochemical and family history data were also retrospectively categorized according to European Atherosclerosis Society (EAS), Simon Broome Register (SBR), Pediatric group of the Italian LIPIGEN (LIPIGEN-FH-PED) and Dutch Lipid Clinic Network (DLCN) criteria. Detailed kindred biochemical and clinical assessments were extended to three generations. The lipid profile was detected by standard laboratory kits, and gene analysis was performed by traditional sequencing or Next-Generation Sequencing (NGS).

RESULTS

Among 180 hypercholesterolemic subjects, FH suspected based on the above criteria, 164/180 had the diagnosis confirmed, showing causative mutations. The mutation detection rate (MDR) was 91.1%. The scoring criteria proposed by the EAS, SBR and LIPIGEN-FH-PED (resulting in high probable, possible-defined and probable-defined, respectively) showed high sensitivity (~90%), low specificity (~6%) and high MDR (~91%). It is noteworthy that their application, as a discriminant for the execution of the molecular investigation, would lead to a loss of 9.1%, 9.8% and 9.1%, respectively, of FH-affected patients, as confirmed by the genetic analysis. DLCN criteria, for which LDL-C cut-offs are not specific for childhood, would lead to a loss of 53% of patients with mutations.

CONCLUSIONS

In the pediatric population, the combination of LDL-C ≥95th percentile in the proband and the dominant inheritance pattern of hypercholesterolemia, with LDL-C ≥95th percentile in one parent, is a simple, useful and effective diagnostic criterion, showing high MDR. This pattern is crucial for early FH diagnosis. EAS, SBR and LIPIGEN-FH-PED criteria can underestimate the real number of patients with gene mutations and cannot be considered strictly discriminant for the execution of molecular analysis.

Impact of 12-SNP and 6-SNP Polygenic Scores on Predisposition to High LDL-Cholesterol Levels in Patients with Familial Hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) comprises high LDL-cholesterol (LDL-c) levels and high cardiovascular disease risk. In the absence of pathogenic variants in causative genes, a polygenic basis was hypothesized.

METHODS

In a population of 418 patients (excluding homozygotes) with clinical suspicion of FH, the FH-causative genes and the regions of single nucleotide polymorphisms (SNPs) included in 12-SNP and 6-SNP scores were sequenced by next-generation sequencing, allowing for the detection of pathogenic variants (V+) in 220 patients. To make a comparison, only patients without uncertain significance variants (V-/USV-) were considered (n = 162).

RESULTS

Higher values of both scores were observed in V+ than in V-. Considering a cut-off leading to 80% of V-/USV- as score-positive, a lower prevalence of patients positive for both 12-SNP and 6-SNP scores was observed in V+ (p = 0.010 and 0.033, respectively). Mainly for the 12-SNP score, among V+ patients, higher LDL-c levels were observed in score-positive (223 mg/dL -IQR 187-279) than in negative patients (212 mg/dL -IQR 162-240; p = 0.006). Multivariate analysis confirmed the association of scores and LDL-c levels independently of age, sex, and presence of pathogenic variants and revealed a greater association in children.

CONCLUSIONS

The 12-SNP and 6-SNP polygenic scores could explain hypercholesterolemia in patients without pathogenic variants as well as the variability of LDL-c levels among patients with FH-causative variants.

Significant but partial lipoprotein lipase functional loss caused by a novel occurrence of rare LPL biallelic variants

BACKGROUND

Lipoprotein lipase (LPL) plays a crucial role in triglyceride hydrolysis. Rare biallelic variants in the LPL gene leading to complete or near-complete loss of function cause autosomal recessive familial chylomicronemia syndrome. However, rare biallelic LPL variants resulting in significant but partial loss of function are rarely documented. This study reports a novel occurrence of such rare biallelic LPL variants in a Chinese patient with hypertriglyceridemia-induced acute pancreatitis (HTG-AP) during pregnancy and provides an in-depth functional characterization.

METHODS

The complete coding sequences and adjacent intronic regions of the LPL, APOC2, APOA5, LMF1, and GPIHBP1 genes were analyzed by Sanger sequencing. The aim was to identify rare variants, including nonsense, frameshift, missense, small in-frame deletions or insertions, and canonical splice site mutations. The functional impact of identified LPL missense variants on protein expression, secretion, and activity was assessed in HEK293T cells through single and co-transfection experiments, with and without heparin treatment.

RESULTS

Two rare LPL missense variants were identified in the patient: the previously reported c.809G > A (p.Arg270His) and a novel c.331G > C (p.Val111Leu). Genetic testing confirmed these variants were inherited biallelically. Functional analysis showed that the p.Arg270His variant resulted in a near-complete loss of LPL function due to effects on protein synthesis/stability, secretion, and enzymatic activity. In contrast, the p.Val111Leu variant retained approximately 32.3% of wild-type activity, without impacting protein synthesis, stability, or secretion. Co-transfection experiments indicated a combined activity level of 20.7%, suggesting no dominant negative interaction between the variants. The patient's post-heparin plasma LPL activity was about 35% of control levels.

CONCLUSIONS

This study presents a novel case of partial but significant loss-of-function biallelic LPL variants in a patient with HTG-AP during pregnancy. Our findings enhance the understanding of the nuanced relationship between LPL genotypes and clinical phenotypes, highlighting the importance of residual LPL function in disease manifestation and severity. Additionally, our study underscores the challenges in classifying partial loss-of-function variants in classical Mendelian disease genes according to the American College of Medical Genetics and Genomics (ACMG)'s variant classification guidelines.

Reproductive Carrier Screening: Identifying Families at Risk for Familial Hypercholesterolemia in the United States

BACKGROUND

Familial hypercholesterolemia is a treatable genetic condition but remains underdiagnosed. We reviewed the frequency of pathogenic or likely pathogenic (P/LP) variants in the LDLR gene in female individuals receiving reproductive carrier screening.

METHODS

This retrospective observational study included samples from female patients (aged 18-55 years) receiving a 274-gene carrier screening panel from January 2020 to September 2022. LDLR exons and their 10 base pair flanking regions were sequenced. Carrier frequency for P/LP variants was calculated for the entire population and by race/ethnicity. The most common variants and their likely functional effects were evaluated.

RESULTS

A total of 91 637 tests were performed on women with race/ethnicity reported as Asian (8.8%), Black (6.1%), Hispanic (8.5%), White (29.0%), multiple or other (15.0%), and missing (33.0%). Median age was 32.8 years with 83 728 (91%) <40 years. P/LP LDLR variants were identified in 283 samples (1 in 324). No patients were identified with >1 P/LP variant. LDLR carrier frequency was higher in Asian (1 in 191 [95% CI, 1 in 142-258]) compared with White (1 in 417 [95% CI, 1 in 326-533]; P<0.001) or Black groups (1 in 508 [95% CI, 1 in 284-910]; P=0.004). The most common variants differed between populations. Of all variants, at least 25.0% were predicted as null variants.

CONCLUSIONS

P/LP variants in LDLR are common. Expanding the use of reproductive carrier screening to include genes associated with FH presents another opportunity to identify people predisposed to cardiovascular disease.

Development and utility of a clinical research informatics application for participant recruitment and workflow management for a return of results pilot trial in familial hypercholesterolemia in the Million Veteran Program

Objective

The development of clinical research informatics tools and workflow processes associated with re-engaging biobank participants has become necessary as genomic repositories increasingly consider the return of actionable research results.

Materials and Methods

Here we describe the development and utility of an informatics application for participant recruitment and enrollment management for the Veterans Affairs Million Veteran Program Return Of Actionable Results Study, a randomized controlled pilot trial returning individual genetic results associated with familial hypercholesterolemia.

Results

The application is developed in Python-Flask and was placed into production in November 2021. The application includes modules for chart review, medication reconciliation, participant contact and biospecimen logging, survey recording, randomization, and documentation of genetic counseling and result disclosure. Three primary users, a genetic counselor and two research coordinators, and 326 Veteran participants have been integrated into the system as of February 23, 2023. The application has successfully handled 3367 task requests involving greater than 95 000 structured data points. Specifically, application users have recorded 326 chart reviews, 867 recruitment telephone calls, 158 telephone-based surveys, and 61 return of results genetic counseling sessions, among other available study tasks.

Conclusion

The development of usable, customizable, and secure informatics tools will become increasingly important as large genomic repositories begin to return research results at scale. Our work provides a proof-of-concept for developing and using such tools to aid in managing the return of results process within a national biobank.

Identification of a novel LDLR p.Glu179Met variant in Thai families with familial hypercholesterolemia and response to treatment with PCSK9 inhibitor

Familial hypercholesterolemia (FH) is a genetic disease characterized by elevated LDL-C levels. In this study, two FH probands and 9 family members from two families from northeastern Thailand were tested for LDLR, APOB, and PCSK9 variants by whole-exome sequencing, PCR-HRM, and Sanger sequencing. In silico analysis of LDLR was performed to analyse its structure‒function relationship. A novel variant of LDLR (c.535_536delinsAT, p.Glu179Met) was detected in proband 1 and proband 2 in homozygous and heterozygous forms, respectively. A total of 6 of 9 family members were heterozygous for LDLR p.Glu179Met variant. Compared with proband 2, proband 1 had higher baseline TC and LDL-C levels and a poorer response to lipid-lowering therapy combined with a PCSK9 inhibitor. Multiple sequence alignment showed that LDLR p.Glu179Met was located in a fully conserved region. Homology modelling demonstrated that LDLR p.Glu179Met variant lost one H-bond and a negative charge. In conclusion, a novel LDLR p.Glu179Met variant was identified for the first time in Thai FH patients. This was also the first report of homozygous FH patient in Thailand. Our findings may expand the knowledge of FH-causing variants in Thai population, which is beneficial for cascade screening, genetic counselling, and FH management to prevent coronary artery disease.

Tracking updates in clinical databases increases efficiency for variant reanalysis

Purpose

Variant interpretation, guided by American College of Medical Genetics and Genomics guidelines, can inform clinical decision-making. However, interpretations may change over time for a variety of reasons. Periodic reanalysis of previous variant interpretations is important to ensure that reported genetic findings remain accurate according to current knowledge.

Methods

We performed automated filtering by comparing ClinVar variants available in August 2020 with those from August 2021 to screen for potential reanalysis candidates from 3 projects. These variants were subsequently interpreted based on the American College of Medical Genetics and Genomics/Association for Molecular Pathology variant interpretation guideline or ClinGen revised gene-specific guidelines if applicable.

Results

Our method annotated 241 unique variants requiring reanalysis, from 3 projects containing 3,832,210 previously interpreted variants, including those filtered automatically. Among these 241 variants, 43 variants changed interpretation, including 55.81% (N = 24) with upgraded and 44.19% (N = 19) with downgraded classifications. An efficiency study showed that our strategy increased the reanalysis efficiency and saved reviewing time.

Conclusion

We demonstrated an effective high-throughput method, initiating from external data updates, to achieve variant reanalysis in a clinical laboratory. This filtering method reduced the number of variants that need to be reanalyzed, screened potential variants, and saved time and cost for clinical laboratories.

The Expansion of Genetic Testing in Cardiovascular Medicine: Preparing the Cardiology Community for the Changing Landscape

PURPOSE OF REVIEW

Pathogenic DNA variants underlie many cardiovascular disease phenotypes. The most well-recognized of these include familial dyslipidemias, cardiomyopathies, arrhythmias, and aortopathies. The clinical presentations of monogenic forms of cardiovascular disease are often indistinguishable from those with complex genetic and non-genetic etiologies, making genetic testing an essential aid to precision diagnosis.

RECENT FINDINGS

Precision diagnosis enables efficient management, appropriate use of emerging targeted therapies, and follow-up of at-risk family members. Genetic testing for these conditions is widely available but under-utilized. In this review, we summarize the potential benefits of genetic testing, highlighting the specific cardiovascular disease phenotypes in which genetic testing should be considered, and how clinicians can integrate guideline-directed genetic testing into their practice.

Evaluating ClinGen variant curation expert panels' application of PVS1 code

BACKGROUND

The 2015 American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology (AMP) guidelines articulates that the effects of certain types of variants on gene function can often be seen as a complete absence of the gene product by leading to a lack of transcription or nonsense-mediated decay(NMD). However, detailed information considering different types of loss of function(LOF) variants, refined steps assimilating details concerning location of variant, changes in strength levels, NMD boundary, or any additional information pointing to a true null effect, were all left to expert judgement. As part of its Clinical Genome Resource (ClinGen) initiative, Variant Curation Expert Panels (VCEPs) are designated to make gene/disease-centric specifications in accordance with the ACMG/AMP guidelines, including a more detailed definition of what constitutes an appropriate LOF evidence. Our goal was to evaluate the current LOF guidelines developed by the VCEPs and analyse the prior curated variants concerning the PVS1 criteria, bringing people occupied in genetic data analysis a comprehensive understanding of this code.

METHODS

Our study evaluated 7 VCEPs for their LOF criteria (PVS1). Subsequently, we assessed the predictive criteria by considering the underlying disease mechanism, protein transcript, and variant types delineated. Then, we meticulously curated the LOF evidence referenced by each VCEP in their preliminary variant classification, thereby scrutinizing the recommendations put forth by VCEPs and their application in the interpretation of the aforementioned predictive criteria. Based on these, an extensive curation of evidence summary considering PVS1 applied by VCEPs according to their classification of pilot variants for the purpose of analyzing VCEP criteria specifications and their use in the understanding of LOF was conducted.

RESULTS

We observed in this article that the VCEPs discussed followed the majority of Sequence Variant Interpretation (SVI) recommendations concerning the application of this LOF criteria, except for some disease/gene specific considerations. We highlighted the wide range of PVS1 strength levels approved by VCEP, reflecting the diversity of evidence for each variants type. In addition, we observed substantial differences in the approach used to determine relative strengths for different types of null variants and in the attitude towards these principles concerning variant location, NMD and influence to protein function between VCEPs.

CONCLUSIONS

It is difficult to understand the intricacies of the predictive data(PVS1), which often requires expert-level knowledge of disease/gene. The VCEP criteria specifications for the predictive evidence play an important role in making it more accessible for the curators to apply the predictive data by providing details concerning this complex criteria. Despite this, we believe there is a need for more guidance on standardizing this process and ensuring consistency in the application of this predictive evidence.

Unraveling the genetic background of individuals with a clinical familial hypercholesterolemia phenotype

Familial hypercholesterolemia (FH) is a common genetic disorder of lipid metabolism caused by pathogenic/likely pathogenic variants in LDLR, APOB, and PCSK9 genes. Variants in FH-phenocopy genes (LDLRAP1, APOE, LIPA, ABCG5, and ABCG8), polygenic hypercholesterolemia, and hyperlipoprotein (a) [Lp(a)] can also mimic a clinical FH phenotype. We aim to present a new diagnostic tool to unravel the genetic background of clinical FH phenotype. Biochemical and genetic study was performed in 1,005 individuals with clinical diagnosis of FH, referred to the Portuguese FH Study. A next-generation sequencing panel, covering eight genes and eight SNPs to determine LDL-C polygenic risk score and LPA genetic score, was validated, and used in this study. FH was genetically confirmed in 417 index cases: 408 heterozygotes and 9 homozygotes. Cascade screening increased the identification to 1,000 FH individuals, including 11 homozygotes. FH-negative individuals (phenotype positive and genotype negative) have Lp(a) >50 mg/dl (30%), high polygenic risk score (16%), other monogenic lipid metabolism disorders (1%), and heterozygous pathogenic variants in FH-phenocopy genes (2%). Heterozygous variants of uncertain significance were identified in primary genes (12%) and phenocopy genes (7%). Overall, 42% of our cohort was genetically confirmed with FH. In the remaining individuals, other causes for high LDL-C were identified in 68%. Hyper-Lp(a) or polygenic hypercholesterolemia may be the cause of the clinical FH phenotype in almost half of FH-negative individuals. A small part has pathogenic variants in ABCG5/ABCG8 in heterozygosity that can cause hypercholesterolemia and should be further investigated. This extended next-generation sequencing panel identifies individuals with FH and FH-phenocopies, allowing to personalize each person's treatment according to the affected pathway.

ACMG/AMP variant classification framework in arginase 1 deficiency: Implications for birth prevalence estimates and diagnostics

Purpose

Arginase 1 (ARG1) deficiency manifests with hyperargininemia and progressive neurological impairment. Recent estimates of birth prevalence using allele frequencies of ARG1 variants do not sufficiently distinguish benign from pathogenic variants. Additionally, ongoing discussions of reproductive carrier screening for diseases such as ARG1 creates a need for improved understanding of ARG1 variant classification. Here, we incorporate American College of Medical Genetics and Genomics/Association for Molecular Pathology-developed guidelines for interpreting gene variants and in silico predictions to select allele frequencies for estimation of global birth prevalence of ARG1 deficiency.

Methods

We interrogated Genome Aggregation Database and PubMed for published (defined as identified in patients with clinically defined arginase deficiency in scientific literature, n = 73) and unpublished ARG1 variants (defined as variants present in Genome Aggregation Database, unique to ARG1, but not yet associated with clinical arginase deficiency, n = 302). American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines were applied to classify variants using Franklin Genoox artificial intelligence-powered platform and manual review.

Results

Of 73 published ARG1 variants, 16 classified as pathogenic, 30 as likely pathogenic, and 27 as variant of uncertain significance. Of 302 unpublished ARG1 variants, 3 classified as pathogenic, 28 likely pathogenic, and 229 variant of uncertain significance. Mutant allele frequency estimates ranged from 17 to 266 per 100,000 and birth prevalence from 1 in 141,331 to 34,602,076.

Conclusion

We show that a large proportion of ARG1 variants lack adequate evidence of pathogenicity. These findings underscore the significance of functional studies and accumulating clinical data for determination of variant pathogenicity and for improved understanding of global birth prevalence of ARG1 deficiency.

Novel LDLR variants affecting low density lipoprotein metabolism identified in familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant disease of lipid metabolism mainly caused by mutations in the low-density lipoprotein receptor (LDLR) gene. Genetic detection of patients with FH help with precise diagnosis and treatment, thus reducing the risk of coronary heart disease (CHD) and other related diseases. The study aimed to identify the causative gene mutations in a Chinese FH family and reveal the pathogenicity and the mechanism of these mutations.

METHODS AND RESULTS

Whole exome sequencing was performed in a patient with severe lipid metabolism dysfunction seeking fertility guidance from a Chinese FH family. Two LDLR variants c.1875 C > G (p.N625K; novel variant) and c.1448G > A (p.W483*) were identified in the family. Wildtype and mutant LDLR constructs were established by the site-direct mutagenesis technique. Functional studies were carried out by cell transfection to evaluate the impact of detected variants on LDLR activity. The two variants were proven to affect LDL uptake and binding, resulting in cholesterol clearance reduction to different degrees. According to The American College of Medical Genetics and Genomics (ACMG) Standards and Guidelines, the W483* variant was classified as "Pathogenic", while the N625K variant as "VUS".

CONCLUSIONS

Our results provide novel experimental evidence of functional alteration by LDLR variants identified in our study and expand the mutational spectrum of LDLR mutation induced FH.

Stratification in Heterozygous Familial Hypercholesterolemia: Imaging, Biomarkers, and Genetic Testing

PURPOSE OF REVIEW

Heterozygous familial hypercholesterolemia (HeFH) is the most common monogenic autosomal dominant disorder. However, the condition is often underdiagnosed and undertreated. The objective of this review is to provide an update on the risk stratification in patients with HeFH, incorporating new cardiovascular imaging techniques, various biomarkers, and genetic studies.

RECENT FINDINGS

The diagnosis of HeFH places patients in a high cardiovascular risk category due to the increased incidence of premature atherosclerotic cardiovascular disease. However, the level of risk varies significantly among different individuals with HeFH. Achieving an optimal stratification of cardiovascular risk is crucial for establishing appropriate and accurate treatment and management strategies. Different new tools such as risk scores have emerged in recent years, aiding physicians in assessing the risk stratification for HeFH using imaging, biomarkers, and genetics. This review emphasizes that not all patients with HeFH face the same cardiovascular risk. By utilizing different assessment tools, we can identify those who require more intensive monitoring, follow-up, and treatment.

Deep generative models of LDLR protein structure to predict variant pathogenicity

The complex structure and function of low density lipoprotein receptor (LDLR) makes classification of protein-coding missense variants challenging. Deep generative models, including Evolutionary model of Variant Effect (EVE), Evolutionary Scale Modeling (ESM), and AlphaFold 2 (AF2), have enabled significant progress in the prediction of protein structure and function. ESM and EVE directly estimate the likelihood of a variant sequence but are purely data-driven and challenging to interpret. AF2 predicts LDLR structures, but variant effects are explicitly modeled by estimating changes in stability. We tested the effectiveness of these models for predicting variant pathogenicity compared to established methods. AF2 produced two distinct conformations based on a novel hinge mechanism. Within ESM's hidden space, benign and pathogenic variants had different distributions. In EVE, these distributions were similar. EVE and ESM were comparable to Polyphen-2, SIFT, REVEL, and Primate AI for predicting binary classifications in ClinVar. However, they were more strongly correlated with experimental measures of LDL uptake. AF2 poorly performed in these tasks. Using the UK Biobank to compare association with clinical phenotypes, ESM and EVE were more strongly associated with serum LDL-C than Polyphen-2. ESM was able to identify variants with more extreme LDL-C levels than EVE and had a significantly stronger association with atherosclerotic cardiovascular disease. In conclusion, AF2 predicted LDLR structures do not accurately model variant pathogenicity. ESM and EVE are competitive with prior scoring methods for prediction based on binary classifications in ClinVar but are superior based on correlations with experimental assays and clinical phenotypes.

Polygenic risk for triglyceride levels in the presence of a high impact rare variant

BACKGROUND

Elevated triglyceride (TG) levels are a heritable and modifiable risk factor for cardiovascular disease and have well-established associations with common genetic variation captured in a polygenic risk score (PRS). In young adulthood, the 22q11.2 microdeletion conveys a 2-fold increased risk for mild-moderate hypertriglyceridemia. This study aimed to assess the role of the TG-PRS in individuals with this elevated baseline risk for mild-moderate hypertriglyceridemia.

METHODS

We studied a deeply phenotyped cohort of adults (n = 157, median age 34 years) with a 22q11.2 microdeletion and available genome sequencing, lipid level, and other clinical data. The association between a previously developed TG-PRS and TG levels was assessed using a multivariable regression model adjusting for effects of sex, BMI, and other covariates. We also constructed receiver operating characteristic (ROC) curves using logistic regression models to assess the ability of TG-PRS and significant clinical variables to predict mild-moderate hypertriglyceridemia status.

RESULTS

The TG-PRS was a significant predictor of TG-levels (p = 1.52E-04), along with male sex and BMI, in a multivariable model (pmodel = 7.26E-05). The effect of TG-PRS appeared to be slightly stronger in individuals with obesity (BMI ≥ 30) (beta = 0.4617) than without (beta = 0.1778), in a model unadjusted for other covariates (p-interaction = 0.045). Among ROC curves constructed, the inclusion of TG-PRS, sex, and BMI as predictor variables produced the greatest area under the curve (0.749) for classifying those with mild-moderate hypertriglyceridemia, achieving an optimal sensitivity and specificity of 0.746 and 0.707, respectively.

CONCLUSIONS

These results demonstrate that in addition to significant effects of sex and BMI, genome-wide common variation captured in a PRS also contributes to the variable expression of the 22q11.2 microdeletion with respect to elevated TG levels.

Modelling a two-stage adult population screen for autosomal dominant familial hypercholesterolaemia: cross-sectional analysis within the UK Biobank

Background

Most people with autosomal dominant familial hypercholesterolaemia (FH) remain undetected, which represents a missed opportunity for coronary heart disease prevention.

Objective

To evaluate the performance of two-stage adult population screening for FH.

Design

Using data from UK Biobank, we estimated the screening performance of different low-density lipoprotein cholesterol (LDL-C) cut-offs (stage 1) to select adults for DNA sequencing (stage 2) to identify individuals with FH-causing variants in LDLR, APOB, PCSK9 and APOE. We estimated the number of additional FH cases detected by cascade testing of first-degree relatives of index cases and compared the overall approach with screening in childhood.

Setting

UK Biobank.

Participants

140 439 unrelated participants of European ancestry from UK Biobank with information on circulating LDL-C concentration and exome sequence.

Main outcome measures

For different LDL-C cut-offs, we estimated the detection and false-positive rate, the proportion of individuals who would be referred for DNA sequencing (stage 1 screen positive rate), and the number of FH cases identified by population screening followed by cascade testing.

Results

We identified 488 individuals with an FH-causing variant and 139 951 without (prevalence 1 in 288). An LDL-C cut-off of >4.8 mmol/L had a stage 1 detection rate (sensitivity) of 40% (95% CI 36 to 44%) for a false-positive rate of 10% (95% CI 10 to 11%). Detection rate increased at lower LDL-C cut-offs but at the expense of higher false-positive and screen positive rates, and vice versa. Two-stage screening of 100 000 adults using an LDL-C cut-off of 4.8 mmol/L would generate 10 398 stage 1 screen positives for sequencing, detect 138 FH cases and miss 209. Up to 207 additional cases could be detected through two-generation cascade testing of first-degree relatives. By comparison, based on previously published data, childhood screening followed by cascade testing was estimated to detect nearly three times as many affected individuals for around half the sequencing burden.

Conclusions

Two-stage adult population screening for FH could help achieve the 25% FH case detection target set in the National Health Service Long Term Plan, but less efficiently than childhood screening and with a greater sequencing requirement.

How human genetic context can inform pathogenicity classification: FGFR1 variation in idiopathic hypogonadotropic hypogonadism

Precision medicine requires precise genetic variant interpretation, yet many disease-associated genes have unresolved variants of unknown significance (VUS). We analyzed variants in a well-studied gene, FGFR1, a common cause of Idiopathic Hypogonadotropic Hypogonadism (IHH) and examined whether regional genetic enrichment of missense variants could improve variant classification. FGFR1 rare sequence variants (RSVs) were examined in a large cohort to (i) define regional genetic enrichment, (ii) determine pathogenicity based on the American College of Medical Genetics/Association for Molecular Pathology (ACMG/AMP) variant classification framework, and (iii) characterize the phenotype of FGFR1 variant carriers by variant classification. A total of 143 FGFR1 RSVs were identified in 175 IHH probands (n = 95 missense, n = 48 protein-truncating variants). FGFR1 missense RSVs showed regional enrichment across biologically well-defined domains: D1, D2, D3, and TK domains and linker regions (D2-D3, TM-TK). Using these defined regions of enrichment to augment the ACMG/AMP classification reclassifies 37% (20/54) of FGFR1 missense VUS as pathogenic or likely pathogenic (PLP). Non-proband carriers of FGFR1 missense VUS variants that were reclassified as PLP were more likely to express IHH or IHH-associated phenotypes [anosmia or delayed puberty] than non-proband carriers of FGFR1 missense variants that remained as VUS (76.9% vs 34.7%, p = 0.035). Using the largest cohort of FGFR1 variant carriers, we show that integration of regional genetic enrichment as moderate evidence for pathogenicity improves the classification of VUS and that reclassified variants correlated with phenotypic expressivity. The addition of regional genetic enrichment to the ACMG/AMP guidelines may improve clinical variant interpretation.

Refinement of the diagnostic approach for the identification of children and adolescents affected by familial hypercholesterolemia: Evidence from the LIPIGEN study

BACKGROUND AND AIMS

We aimed to describe the limitations of familiar hypercholesterolemia (FH) diagnosis in childhood based on the presence of the typical features of FH, such as physical sings of cholesterol accumulation and personal or family history of premature cardiovascular disease or hypercholesterolemia, comparing their prevalence in the adult and paediatric FH population, and to illustrate how additional information can lead to a more effective diagnosis of FH at a younger age.

METHODS

From the Italian LIPIGEN cohort, we selected 1188 (≥18 years) and 708 (<18 years) genetically-confirmed heterozygous FH, with no missing personal FH features. The prevalence of personal and familial FH features was compared between the two groups. For a sub-group of the paediatric cohort (N = 374), data about premature coronary heart disease (CHD) in second-degree family members were also included in the evaluation.

RESULTS

The lower prevalence of typical FH features in children/adolescents vs adults was confirmed: the prevalence of tendon xanthoma was 2.1% vs 13.1%, and arcus cornealis was present in 1.6% vs 11.2% of the cohorts, respectively. No children presented clinical history of premature CHD or cerebral/peripheral vascular disease compared to 8.8% and 5.6% of adults, respectively. The prevalence of premature CHD in first-degree relatives was significantly higher in adults compared to children/adolescents (38.9% vs 19.7%). In the sub-cohort analysis, a premature CHD event in parents was reported in 63 out of 374 subjects (16.8%), but the percentage increased to 54.0% extending the evaluation also to second-degree relatives.

CONCLUSIONS

In children, the typical FH features are clearly less informative than in adults. A more thorough data collection, adding information about second-degree relatives, could improve the diagnosis of FH at younger age.

Predictive Modeling and Structure Analysis of Genetic Variants in Familial Hypercholesterolemia: Implications for Diagnosis and Protein Interaction Studies

PURPOSE OF REVIEW

Familial hypercholesterolemia (FH) is a hereditary condition characterized by elevated levels of low-density lipoprotein cholesterol (LDL-C), which increases the risk of cardiovascular disease if left untreated. This review aims to discuss the role of bioinformatics tools in evaluating the pathogenicity of missense variants associated with FH. Specifically, it highlights the use of predictive models based on protein sequence, structure, evolutionary conservation, and other relevant features in identifying genetic variants within LDLR, APOB, and PCSK9 genes that contribute to FH.

RECENT FINDINGS

In recent years, various bioinformatics tools have emerged as valuable resources for analyzing missense variants in FH-related genes. Tools such as REVEL, Varity, and CADD use diverse computational approaches to predict the impact of genetic variants on protein function. These tools consider factors such as sequence conservation, structural alterations, and receptor binding to aid in interpreting the pathogenicity of identified missense variants. While these predictive models offer valuable insights, the accuracy of predictions can vary, especially for proteins with unique characteristics that might not be well represented in the databases used for training. This review emphasizes the significance of utilizing bioinformatics tools for assessing the pathogenicity of FH-associated missense variants. Despite their contributions, a definitive diagnosis of a genetic variant necessitates functional validation through in vitro characterization or cascade screening. This step ensures the precise identification of FH-related variants, leading to more accurate diagnoses. Integrating genetic data with reliable bioinformatics predictions and functional validation can enhance our understanding of the genetic basis of FH, enabling improved diagnosis, risk stratification, and personalized treatment for affected individuals. The comprehensive approach outlined in this review promises to advance the management of this inherited disorder, potentially leading to better health outcomes for those affected by FH.

Specifications of the ACMG/AMP guidelines for ACADVL variant interpretation

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency (VLCADD) is a relatively common inborn error of metabolism, but due to difficulty in accurately predicting affected status through newborn screening, molecular confirmation of the causative variants by sequencing of the ACADVL gene is necessary. Although the ACMG/AMP guidelines have helped standardize variant classification, ACADVL variant classification remains disparate due to a phenotype that can be nonspecific, the possibility of variants that produce late-onset disease, and relatively high carrier frequency, amongst other challenges. Therefore, an ACADVL-specific variant curation expert panel (VCEP) was created to facilitate the specification of the ACMG/AMP guidelines for VLCADD. We expect these guidelines to help streamline, increase concordance, and expedite the classification of ACADVL variants.