Carrier screening for Gaucher disease: lessons for low-penetrance, treatable diseases

Evaluating the association of biallelic OGDHL variants with significant phenotypic heterogeneity

BACKGROUND

Biallelic variants in OGDHL, encoding part of the α-ketoglutarate dehydrogenase complex, have been associated with highly heterogeneous neurological and neurodevelopmental disorders. However, the validity of this association remains to be confirmed. A second OGDHL patient cohort was recruited to carefully assess the gene-disease relationship.

METHODS

Using an unbiased genotype-first approach, we screened large, multiethnic aggregated sequencing datasets worldwide for biallelic OGDHL variants. We used CRISPR/Cas9 to generate zebrafish knockouts of ogdhl, ogdh paralogs, and dhtkd1 to investigate functional relationships and impact during development. Functional complementation with patient variant transcripts was conducted to systematically assess protein functionality as a readout for pathogenicity.

RESULTS

A cohort of 14 individuals from 12 unrelated families exhibited highly variable clinical phenotypes, with the majority of them presenting at least one additional variant, potentially accounting for a blended phenotype and complicating phenotypic understanding. We also uncovered extreme clinical heterogeneity and high allele frequencies, occasionally incompatible with a fully penetrant recessive disorder. Human cDNA of previously described and new variants were tested in an ogdhl zebrafish knockout model, adding functional evidence for variant reclassification. We disclosed evidence of hypomorphic alleles as well as a loss-of-function variant without deleterious effects in zebrafish variant testing also showing discordant familial segregation, challenging the relationship of OGDHL as a conventional Mendelian gene. Going further, we uncovered evidence for a complex compensatory relationship among OGDH, OGDHL, and DHTKD1 isoenzymes that are associated with neurodevelopmental disorders and exhibit complex transcriptional compensation patterns with partial functional redundancy.

CONCLUSIONS

Based on the results of genetic, clinical, and functional studies, we formed three hypotheses in which to frame observations: biallelic OGDHL variants lead to a highly variable monogenic disorder, variants in OGDHL are following a complex pattern of inheritance, or they may not be causative at all. Our study further highlights the continuing challenges of assessing the validity of reported disease-gene associations and effects of variants identified in these genes. This is particularly more complicated in making genetic diagnoses based on identification of variants in genes presenting a highly heterogenous phenotype such as "OGDHL-related disorders".

Ambroxol as a disease-modifying treatment to reduce the risk of cognitive impairment in GBA-associated Parkinson's disease: a multicentre, randomised, double-blind, placebo-controlled, phase II trial. The AMBITIOUS study protocol

Background

Heterozygous mutations in the GBA gene, encoding the lysosomal enzyme β-glucocerebrosidase (GCase), are the most frequent genetic risk factor for Parkinson's disease (PD). GBA-related PD (GBA-PD) patients have higher risk of dementia and reduced survival than non-carriers. Preclinical studies and one open-label trial in humans demonstrated that the chaperone ambroxol (ABX) increases GCase levels and modulates α-synuclein levels in the blood and cerebrospinal fluid (CSF).

Methods and analysis

In this multicentre, double-blind, placebo-controlled, phase II clinical trial, we randomise patients with GBA-PD in a 1:1 ratio to either oral ABX 1.2 g/day or placebo. The duration of treatment is 52 weeks. Each participant is assessed at baseline and weeks 12, 26, 38, 52 and 78. Changes in the Montreal Cognitive Assessment score and the frequency of mild cognitive impairment and dementia between baseline and weeks 52 are the primary outcome measures. Secondary outcome measures include changes in validated scales/questionnaires assessing motor and non-motor symptoms. Neuroimaging features and CSF neurodegeneration markers are used as surrogate markers of disease progression. GCase activity, ABX and α-synuclein levels are also analysed in blood and CSF. A repeated-measures analysis of variance will be used for elaborating results. The primary analysis will be by intention to treat.

Ethics and dissemination

The study and protocols have been approved by the ethics committee of centres. The study is conducted according to good clinical practice and the Declaration of Helsinki. The trial findings will be published in peer-reviewed journals and presented at conferences.

Trial registration numbers

NCT05287503, EudraCT 2021-004565-13.

Insights into the Value of Lyso-Gb1 as a Predictive Biomarker in Treatment-Naïve Patients with Gaucher Disease Type 1 in the LYSO-PROOF Study

Gaucher disease (GD) is a rare autosomal recessive disorder arising from bi-allelic variants in the GBA1 gene, encoding glucocerebrosidase. Deficiency of this enzyme leads to progressive accumulation of the sphingolipid glucosylsphingosine (lyso-Gb1). The international, multicenter, observational "Lyso-Gb1 as a Long-term Prognostic Biomarker in Gaucher Disease"-LYSO-PROOF study succeeded in enrolling a cohort of 160 treatment-naïve GD patients from diverse geographic regions and evaluated the potential of lyso-Gb1 as a specific biomarker for GD. Using genotypes based on established classifications for clinical presentation, patients were stratified into type 1 GD (n = 114) and further subdivided into mild (n = 66) and severe type 1 GD (n = 48). Due to having previously unreported genotypes, 46 patients could not be classified. Though lyso-Gb1 values at enrollment were widely distributed, they displayed a moderate and statistically highly significant correlation with disease severity measured by the GD-DS3 scoring system in all GD patients (r = 0.602, p < 0.0001). These findings support the utility of lyso-Gb1 as a sensitive biomarker for GD and indicate that it could help to predict the clinical course of patients with undescribed genotypes to improve personalized care in the future.

Interventions addressing genetic disease burdens within selected countries in the MENA region: a scoping review

BACKGROUND

The MENA region is disproportionately affected by genetic disease. The aim of this research is to scope the region for evidence of genetic services and public health interventions to identify geographic gaps, and to provide a descriptive overview of interventions to identify knowledge gaps.

METHODS

This study is conducted as a scoping review and follows the Arksey & O'Malley scoping review framework.

RESULTS

Seventy-six articles spanning 16 MENA nations met inclusion criteria. Studies included interventions in the form of genetic service provision (n=28), as well as comprehensive programs including pilot programs (n=7), community-based genetics programs (n=6) national-level prevention programs (n=18), and national-level mandatory programs (n=17).

CONCLUSIONS

There is an imbalanced response to genetic disease burdens across the MENA region. More research is warranted where interventions are scarce, particularly to inform development of pilot community-based programs. There is also a need for better monitoring and evaluation of existing nation-wide programs.

Gaucher Disease Diagnosis Using Lyso-Gb1 on Dry Blood Spot Samples: Time to Change the Paradigm?

For years, the gold standard for diagnosing Gaucher disease (GD) has been detecting reduced β-glucocerebrosidase (GCase) activity in peripheral blood cells combined with GBA1 mutation analysis. The use of dried blood spot (DBS) specimens offers many advantages, including easy collection, the need for a small amount of blood, and simpler transportation. However, DBS has limitations for measuring GCase activity. In this paper, we recount our cross-sectional study and publish seven years of experience using DBS samples and levels of the deacylated form of glucocerebroside, glucosylsphingosine (lyso-Gb1), for GD diagnosis. Of 444 screened subjects, 99 (22.3%) were diagnosed with GD at a median (range) age of 21 (1–78) years. Lyso-Gb levels for genetically confirmed GD patients vs. subjects negative to GD diagnosis were 252 (9–1340) ng/mL and 5.4 (1.5–16) ng/mL, respectively. Patients diagnosed with GD1 and mild GBA1 variants had lower median (range) lyso-Gb1, 194 (9–1050), compared to GD1 and severe GBA1 variants, 447 (38–1340) ng/mL, and neuronopathic GD, 325 (116–1270) ng/mL (p = 0.001). Subjects with heterozygous GBA1 variants (carrier) had higher lyso-Gb1 levels, 5.8 (2.5–15.3) ng/mL, compared to wild-type GBA1, 4.9 (1.5–16), ng/mL (p = 0.001). Lyso-Gb1 levels, median (range), were 5 (2.7–10.7) in heterozygous GBA1 carriers with Parkinson’s disease (PD), similar to lyso-Gb1 levels in subjects without PD. We call for a paradigm change for the diagnosis of GD based on lyso-Gb1 measurements and confirmatory GBA1 mutation analyses in DBS. Lyso-Gb1 levels could not be used to differentiate between heterozygous GBA1 carriers and wild type.

Screening for patients with Gaucher's disease using routine pathology results: PATHFINDER (ferritin, alkaline phosphatase, platelets) study

AIMS

Lysosomal β-glucocerebrosidase A (GBA) deficiency causes Gaucher disease (GD), a recessive disorder caused by bi-allelic mutations in GBA. The prevalence of GD is associated with ethnicity but largely unknown and potentially underestimated in many countries. GD may manifest with organomegaly, bone involvement, and neurological symptoms as well as abnormal laboratory biomarkers. This study attempted to screen for GD in patients using abnormal platelet, alkaline phosphatase (ALP), and ferritin results from laboratory databases.

METHODS

Electronic laboratory databases were interrogated using a 2- to 4-year time interval to identify from clinical biochemistry records patients with a phenotype of reduced platelets (<150 × 10⁹ /L) and either elevated ALP (>130 iu/L) or ferritin [>150 (female) or >250 µg/L (male)]. The mean value over the screening window was used to reduce variability in results. A dried blood spot sample was collected for the determination of GBA activity in patients meeting these criteria. If low GBA activity was found, then the concentration of the GD-specific biomarker glucosyl-sphingosine (lyso-GB1) was assayed, and the GBA gene sequenced.

RESULTS

Samples were obtained from 1058 patients; 232 patients had low GBA activity triggering further analysis. No new cases of GD with homozygosity for pathogenic variants were identified, but 12 patients (1%) were identified to be carriers of a pathogenic variant in GBA.

CONCLUSIONS

Pathology databases hold routine information that can be used to screen for patients with inherited errors of metabolism. However, biochemical screening using mean platelets, ALP, and ferritin has a low yield for unidentified cases of GD.

Family caregivers of rare disease: A survey on health-related quality of life in family caregivers for Gaucher disease patients in China

Background

Rare diseases affect the health‐related quality of life (HRQoL) of patients and their family caregivers (FCs). However, limited evidence is available on the HRQoL of FCs of patients with Gaucher disease (GD). This study aimed to assess HRQoL and related factors among FCs of patients with GD in China.

Methods

A cross‐sectional online survey was conducted with 49 FCs recruited by convenience sampling. Participants completed the Medical Outcome Study Short Form‐36 (SF‐36), Zung's Self‐Rating Anxiety Scale, Zung's Self‐Rating Depression Scale, the Multi‐dimensional Scale of Perceived Social Support, the Herth Hope Index, and a questionnaire about FCs’ and patients’ sociodemographic characteristics. Single‐sample t tests, one‐way analysis of variance, and multivariate linear regression analysis were used to analyze the data analysis.

Results

Participating FCs had significantly lower scores in all eight SF‐36 domains compared with the general population in China (p < 0.01). FCs’ gender, education, daily care time, anxiety, and the perceived disease severity of patients were significant predictors of SF‐36 physical component summary scores. Caregiving help from others, anxiety, perceived disease severity, and medical insurance type were significant predictors of SF‐36 mental component summary scores.

Conclusion

The findings showed FCs of patients with GD had lower HRQoL. There is an urgent need to address the health concerns of FCs of people with rare diseases including their HRQoL.

Impact of Long-Term Enzyme Replacement Therapy on Glucosylsphingosine (Lyso-Gb1) Values in Patients with Type 1 Gaucher Disease: Statistical Models for Comparing Three Enzymatic Formulations

For three decades, enzyme replacement therapy (ERT), and more recently, substrate reduction therapy, have been the standard-of-care for type I Gaucher disease (GD1). Since 2012, three different ERTs have been available. No clinical trial or academic study has ever compared these ERTs beyond one year. Herein we compare the impact of the ERTs on repeated measurements of glucosylsphingosine (lyso-Gb1; the most sensitive and GD-specific biomarker). A total of 135 adult patients (77 (57%) female) with GD1, followed from July 2014 to March 2020 and treated with a single ERT (imiglucerase (n = 41, 30.4%), taliglucerase alfa (n = 21, 15.6%) and velaglucerase alfa (n = 73, 54.1%)), were included. Disease severity was defined by genotypes (mild: N370S (c.1226A>G) homozygous and N370S/R496H (c.1604G) compound heterozygous; severe: all other genotypes) and by the severity score index (SSI; mild: <7; severe: ≥7). Lyso-Gb1 testing was performed at Centogene™ on dry blood spot samples collected during routine visits. Patients treated with imiglucerase had higher lyso-Gb1 levels at different time points. A huge variation in lyso-Gb1 levels was noticeable both inter-individually and intra-individually for all three ERTs. A steeper and faster decrease of lyso-Gb1 levels was shown in velaglucerase alfa. Nevertheless, the differences between medications were not very large, and bigger numbers and more pretreatment data are required for more powerful conclusions.

Toward a fine-scale population health monitoring system

Understanding population health disparities is an essential component of equitable precision health efforts. Epidemiology research often relies on definitions of race and ethnicity, but these population labels may not adequately capture disease burdens and environmental factors impacting specific sub-populations. Here, we propose a framework for repurposing data from electronic health records (EHRs) in concert with genomic data to explore the demographic ties that can impact disease burdens. Using data from a diverse biobank in New York City, we identified 17 communities sharing recent genetic ancestry. We observed 1,177 health outcomes that were statistically associated with a specific group and demonstrated significant differences in the segregation of genetic variants contributing to Mendelian diseases. We also demonstrated that fine-scale population structure can impact the prediction of complex disease risk within groups. This work reinforces the utility of linking genomic data to EHRs and provides a framework toward fine-scale monitoring of population health.

Emerging Targeted Therapeutics for Genetic Subtypes of Parkinsonism

In recent years, a precision medicine approach, which customizes medical treatments based on patients' individual profiles and incorporates variability in genes, the environment, and lifestyle, has transformed medical care in numerous medical fields, most notably oncology. Applying a similar approach to Parkinson's disease (PD) may promote the development of disease-modifying agents that could help slow progression or possibly even avert disease development in a subset of at-risk individuals. The urgent need for such trials partially stems from the negative results of clinical trials where interventions treat all PD patients as a single homogenous group. Here, we review the current obstacles towards the development of precision interventions in PD. We also review and discuss the clinical trials that target genetic forms of PD, i.e., GBA-associated and LRRK2-associated PD.

Outcomes of pregnancies in patients with Gaucher Disease: The experience of a center of excellence on rare metabolic Disease-Gaucher Disease, in Greece

OBJECTIVE

Pregnancy is reported to exacerbate manifestations in women with Gaucher Disease (GD). The objective of our study was to examine the outcome of pregnancies of Caucasian women with GD in a Greek Center of Excellence on GD.

STUDY DESIGN

Fifteen GD women were enrolled. All data were collected by questionnaire: fertility, normal pregnancies, spontaneous-elective-therapeutic abortions, maternal -neonatal status, birth weight and chromosomal abnormalities.

RESULTS

Forty-one pregnancies were reported among 15 women: mean conception age (±SD) 27.7 ± 5.8years (range 17-42years). Thirty-seven conceptions were spontaneous, 4 were after in vitro fertilization (IVF). Twenty three out of the 41 (56.1 %) pregnancies were normal. Eleven out of the 41 (26.8 %) pregnancies resulted in spontaneous abortions, 3 out of 41 (7.3 %) in elective and 3 out of 41 (7.3 %) in therapeutic abortions. Therapeutic abortions were due to worsening of GD manifestations, fetal chromosomal abnormalities and GD type 2 embryo. Nine out of 15 women had maternal complications: gestational diabetes, splenomegaly, hepatomegaly, thrombocytopenia, osteoporosis and postpartum hemorrhage. Twenty three out of the 41 pregnancies resulted in live births. Nine out of the 23 (39.1 %) deliveries were caesarian sections and 14 out of 23 (60.9 %) were vaginal. The total number of neonates was 24 (14 females / 10 males). Mean gestational age on delivery (± SD) was 35.9 ± 3.1 weeks (range 26-38 w). Average female birth weight (±SD) was 2671.4 ± 851.6 g (range 900-4100 grams) and male was 3333 ± 996.4 g (range 1930-4700 grams). Nine out of 24 (37.5 %) neonates had low birth weight. Average low birth weight (±SD) was 1931.1 ± 420.52 g (range 900-2300 grams). Twenty out of the 24 (83.3 %) neonates were healthy. Four out of 24 neonates had neonatal complications: two neonates had GD type 1, one had GD type 3 and one neonate died two days after delivery (it was born at 26 weeks). Four neonates were hospitalized in incubators at the intensive neonatal care unit due to low birth weight. Thirty-nine women did not receive enzyme replacement therapy for GD during pregnancy, while, in two pregnancies, treatment was discontinued during the first trimester and re-administered after that. Mean first menarche age (±SD) was 13.6 ± 0.7 years. Thirteen out of 15 women were menopausal, mean menopausal age (± SD) 466 ± 2.6 years.

CONCLUSION

Most of GD women experience uncomplicated pregnancies and deliver normal, healthy infants, although the rate of complications and the rate of abortions is high in this population.

Precision medicine in Parkinson's disease: emerging treatments for genetic Parkinson's disease

In recent years, numerous clinical trials for disease modification in Parkinson's disease (PD) have failed, possibly because of a "one-size-fits all" approach. Alternatively, a precision medicine approach, which customises treatments based on patients' individual genotype, may help reach disease modification. Here, we review clinical trials that target genetic forms of PD, i.e., GBA-associated and LRRK2-associated PD. In summary, six ongoing studies which explicitely recruit GBA-PD patients, and two studies which recruit LRRK2-PD patients, were identified. Available data on mechanisms of action, study design, and challenges of therapeutic trials are discussed.

Laboratory Diagnosis of Lysosomal Diseases: Newborn Screening to Treatment

The goal of screening programs for inborn errors of metabolism (IEM) is early detection and timely intervention to significantly reduce morbidity, mortality and associated disabilities. Phenylketonuria exemplifies their success as neonates are identified at birth and then promptly treated allowing normal neurological development. Lysosomal diseases comprise about 50 IEM arising from a deficiency in a protein required for proper lysosomal function. Typically, these defects are in lysosomal enzymes with the concomitant accumulation of the enzyme's substrate as the cardinal feature. None of the lysosomal diseases are screened at birth in Australia and in the absence of a family history, traditional laboratory diagnosis of the majority, involves demonstrating a deficiency of the requisite enzyme. Diagnostic confusion can arise from interpretation of the degree of residual enzyme activity causative of disease and is impractical when the disorder is not due to an enzyme deficiency per se. Advances in mass spectrometry technologies has enabled simultaneous measurement of the enzymes' substrates and their metabolites which facilitates the efficiency of diagnosis. Employing urine chemistry as a reflection of multisystemic disease, individual lysosomal diseases can be identified by a characteristic substrate pattern complicit with the enzyme deficiency. Determination of lipids in plasma allows the diagnosis of a further class of lysosomal disorders, the sphingolipids. The ideal goal would be to measure biomarkers for each specific lysosomal disorder in the one mass spectrometry-based platform to achieve a diagnosis. Confirmation of the diagnosis is usually by identifying pathogenic variants in the underlying gene, and although molecular genetic technologies can provide the initial diagnosis, the biochemistry will remain important for interpreting molecular variants of uncertain significance.

How does carrier status for recessive disorders influence reproductive decisions? A systematic review of the literature

Introduction: Carrier screening for recessive disorders is undertaken by prospective parents to inform their reproductive decisions. With the growing availability of affordable and comprehensive expanded carrier screening (ECS), it is expected that carrier screening will become a standard practice in the future. However, the impact of positive carrier screening results on the reproductive decisions of at-risk couples (ARCs) remains underexplored.Areas covered: We performed a systematic literature review to identify peer-reviewed publications describing the reproductive decisions of ARCs. Our search identified 19 relevant publications spanning the period 1994-2018. By synthesizing available evidence, we found that most ARCs chose to prevent the birth of an affected child and the decision to utilize preventive reproductive options was strongly influenced by the clinical nature of a disorder. However, there was also some heterogeneity in reproductive decisions within the same recessive disorders, suggesting that choices of ARCs can be influenced by factors other than the clinical nature of a disorder.Expert opinion: ECS is becoming increasingly common, which will result in the routine identification of many ARCs. Reproductive decision-making by ARCs is a complex and emotionally challenging process, highlighting the critical role of genetic counseling in the care for these potentially vulnerable patients.

Long Term Follow-Up of 103 Untreated Adult Patients with Type 1 Gaucher Disease

The introduction of disease-specific therapy for patients with type I Gaucher disease (GD1) was a revolution in the management of patients, but not without cost. Thus, the management of mildly affected patients is still debated. We herein report a long-term follow-up (median (range) of 20 (5–58) years) of 103 GD1 patients who have never received enzymatic or substrate reduction therapy. The median (range) platelet count and hemoglobin levels in last assessment of all but six patients who refused therapy (although recommended and approved) were 152 (56–408) × 10³/mL and 13.1 (7.6–16.8) g/dL, respectively. Most patients had mild hepatosplenomegaly. Nine patients were splenectomized. No patient developed clinical bone disease. The median (range) lyso-Gb1 levels at last visit was 108.5 (8.1–711) ng/mL; lowest for patients with R496H/other and highest for patients refusing therapy. This rather large cohort with long follow-up confirms that mildly affected patients may remain stable for many years without GD-specific therapy. The challenge for the future, when newborn screening may detect all patients, is to be able to predict which of the early diagnosed patients is at risk for disease-related complications and therefore for early treatment, and who may remain asymptomatic or minimally affected with no need for disease-specific therapy.

Population-based cohort of 500 patients with Gaucher disease in Israel

OBJECTIVE

To characterise a population-based cohort of patients with Gaucher disease (GD) in Israel relative to the general population and describe sociodemographic and clinical differences by disease severity (ie, enzyme replacement therapy [ERT] use).

DESIGN

A cross-sectional study was conducted.

SETTING

Data from the Clalit Health Services electronic health record (EHR) database were used.

PARTICIPANTS

The study population included all patients in the Clalit EHR database identified as having GD as of 30 June 2014.

RESULTS

A total of 500 patients with GD were identified and assessed. The majority were ≥18 years of age (90.6%), female (54.0%), Jewish (93.6%) and 34.8% had high socioeconomic status, compared with 19.0% in the general Clalit population. Over half of patients with GD with available data (51.0%) were overweight/obese and 63.5% had a Charlson Comorbidity Index ≥1, compared with 46.6% and 30.4%, respectively, in the general Clalit population. The majority of patients with GD had a history of anaemia (69.6%) or thrombocytopaenia (62.0%), 40.4% had a history of bone events and 22.2% had a history of cancer. Overall, 41.2% had received ERT.

CONCLUSIONS

Establishing a population-based cohort of patients with GD is essential to understanding disease progression and management. In this study, we highlight the need for physicians to monitor patients with GD regardless of their ERT status.

Computational modelling approaches as a potential platform to understand the molecular genetics association between Parkinson's and Gaucher diseases

Gaucher's disease (GD) is a genetic disorder in which glucocerebroside accumulates in cells and specific organs. It is broadly classified into type I, type II and type III. Patients with GD are at high risk of Parkinson's disease (PD), and the clinical and pathological presentation of GD patients with PD is almost identical to idiopathic PD. Several experimental models like cell culture, animal models, and transgenic mice models were used to understand the molecular mechanism behind GD and PD association; however, such mechanism remains unclear. In this context, based on literature reports, we identified the most common mutations K198T, E326K, T369M, N370S, V394L, D409H, L444P, and R496H, in the Glucosylceramidase (GBA) protein that are known to cause GD1, and represent a risk of developing PD. However, to date, no computational analyses have designed to elucidate the potential functional role of GD mutations with increased risk of PD. The present computational pipeline allows us to understand the structural and functional significance of these GBA mutations with PD. Based on the published data, the most common and severe mutations were E326K, N370S, and L444P, which further selected for our computational analysis. PredictSNP and iStable servers predicted L444P mutant to be the most deleterious and responsible for the protein destabilization, followed by the N370S mutation. Further, we used the structural analysis and molecular dynamics approach to compare the most frequent deleterious mutations (N370S and L444P) with the mild mutation E326K. The structural analysis demonstrated that the location of E326K and N370S in the alpha helix region of the protein whereas the mutant L444P was in the starting region of the beta sheet, which might explain the predicted pathogenicity level and destabilization effect of the L444P mutant. Finally, Molecular Dynamics (MD) at 50 ns showed the highest deviation and fluctuation pattern in the L444P mutant compared to the two mutants E326K and N370S and the native protein. This was consistent with more loss of intramolecular hydrogen bonds and less compaction of the radius of gyration in the L444P mutant. The proposed study is anticipated to serve as a potential platform to understand the mechanism of the association between GD and PD, and might facilitate the process of drug discovery against both GD and PD.

Pre- and post-testing counseling considerations for the provision of expanded carrier screening: exploration of European geneticists' views

Background

Carrier screening is generally performed with the aim of identifying healthy couples at risk of having a child affected with a monogenic disorder to provide them with reproductive options. Expanded carrier screening (ECS), which provides the opportunity for multiple conditions to be screened in one test, offers a more cost-effective and comprehensive option than screening for single disorders. However, implementation of ECS at a population level would have implications for genetic counseling practice.

Methods

We conducted semi-structured interviews with sixteen European clinical and molecular geneticists with expertise in carrier screening to explore their views on the implementation of ECS in the clinical setting.

Results

Using inductive content analysis, we identified content categories relevant to the pre- and post-test settings. Participants believed ECS would ideally be targeted at couples before pregnancy. There was some disagreement regarding the acceptability of performing ECS in individuals, with several participants actively opposing individual-based screening. In addition, participants discussed the importance of ensuring informed and voluntary participation in ECS, recommending measures to minimize external pressure on prospective parents to undergo testing. A need for adequate counseling to foster informed, autonomous reproductive decision-making and provide support for couples found to be at risk was emphasized.

Conclusions

Practical challenges in optimizing pre-test education and post-test counseling should not be underestimated and they should be carefully addressed before implementing ECS in the clinical setting.

Homozygous mutation in TXNRD1 is associated with genetic generalized epilepsy

Increased oxidative stress has been widely implicated in the pathogenesis in various forms of human epilepsy. Here, we report a homozygous mutation in TXNRD1 (thioredoxin reductase 1) in a family with genetic generalized epilepsy. TXNRD1 is an essential selenium-containing enzyme involved in detoxification of reactive oxygen species (ROS) and redox signaling. The TXNRD1 mutation p.Pro190Leu affecting a highly conserved amino acid residue was identified by whole-exome sequencing of blood DNA from the index patient. The detected mutation and its segregation within the family - all siblings of the index patient were homozygous and the parents heterozygous - were confirmed by Sanger sequencing. TXNRD1 activity was determined in subcellular fractions from a skeletal muscle biopsy and skin fibroblasts of the index patient and the expression levels of the mutated protein were assessed by ⁷⁵Se labeling and Western blot analysis. As result of the mutation, the activity of TXNRD1 was reduced in the patient's fibroblasts and skeletal muscle (to 34±3% and 16±8% of controls, respectively). In fibroblasts, we detected reduced ⁷⁵Se-labeling of the enzyme (41±3% of controls). An in-depth in vitro kinetic analysis of the recombinant mutated TXNRD1 indicated 30-40% lowered k_cat/Se values. Therefore, a reduced activity of the enzyme in the patient's tissue samples is explained by (i) lower enzyme turnover and (ii) reduced abundance of the mutated enzyme as confirmed by Western blotting and ⁷⁵Se labeling. The mutant fibroblasts were also found to be less resistant to a hydrogen peroxide challenge. Our data agree with a potential role of insufficient ROS detoxification for disease manifestation in genetic generalized epilepsy.

Children with type 1 Gaucher disease: Changing profiles in the 21st century

Gaucher disease (GD) has phenotypic variability. Increased GD awareness especially among at-risk Ashkenazi Jews (AJ) and availability of non-invasive diagnosis induced trend to prenatal screening. We retrospectively assessed pediatric (<16years) Israeli AJ GD patients to ascertain demographics and phenotype at presentation and over-time because many were identified by large-scale screening. 55/67 patients born since 01/01/2000 are AJ with non-neuronopathic GD: 28 (50.9%) are N370S/N370S; 24 (43.6%) are N370S/other; 3 (3.5%) have no N370S allele. 30 (54.5%) diagnosed by screening; 10 (18.2%) with sibling diagnosed by screening. Of 19 (34.5%) receiving enzyme replacement therapy (ERT), 4/19 (21.1%) were by screening (N370S/N370S; N370S/L444P, N370S/84GG, N370S/IVS2+1); 15/19 (78.9%) diagnosed by symptoms and/or symptomatic sibling. 4/19 (21.1%) began ERT at age <2years; 9/19 (47.4%) at 3-5years; 6/19 (31.6%) at 6-12years. 49% presented with height/weight growth percentiles ≤25%, but group means were comparable up to 12years follow-up including 10 receiving ERT (8 for >5years). 22% presented with anemia, 20% with thrombocytopenia; at last follow-up 4% and 6%, respectively, remained cytopenic. We present a new demographic profile for pediatric GD because many identified by screening had/have few GD signs/symptoms. Nonetheless, early diagnosis is important, especially for non-N370S, non-mild genotypes.

Defects in trafficking bridge Parkinson's disease pathology and genetics

Parkinson's disease is a debilitating, age-associated movement disorder. A central aspect of the pathophysiology of Parkinson's disease is the progressive demise of midbrain dopamine neurons and their axonal projections, but the underlying causes of this loss are unclear. Advances in genetics and experimental model systems have illuminated an important role for defects in intracellular transport pathways to lysosomes. The accumulation of altered proteins and damaged mitochondria, particularly at axon terminals, ultimately might overwhelm the capacity of intracellular disposal mechanisms. Cell-extrinsic mechanisms, including inflammation and prion-like spreading, are proposed to have both protective and deleterious functions in Parkinson's disease.

Designing expanded carrier screening panels: results of a qualitative study with European geneticists

Aim: To explore the views of clinical and molecular geneticists on the inclusion of disorders and specific pathogenic mutations into expanded carrier screening (ECS) tests for reproductive purposes. Materials & methods: In-depth semistructured interviews were conducted with 16 European geneticists between April and September 2014. Results: All participants supported carrier screening for severe, childhood-onset autosomal recessive disorders with known natural history. Some participants were also in favor of screening for late-onset and X-linked disorders. Regarding selection of specific pathogenic mutations, our participants argued that ECS should include highly penetrant pathogenic mutations with known genotype–phenotype associations. Conclusion: This study highlights main challenges surrounding the development of ECS panels and offers suggestions for future research in this rapidly advancing field.

Gaucher disease epidemiology and natural history: a comprehensive review of the literature

OBJECTIVES

The objectives of this research were: (1) to heighten awareness of Gaucher disease (GD), a rare lysosomal storage disorder with highly heterogeneous patterns of organ involvement and disease severity, to clinicians most likely to encounter these patients, and; (2) to summarize the published evidence on GD epidemiology which is essential to accurately depict the total societal burden of this rare worldwide disorder.

METHODS

A comprehensive literature review was undertaken to summarize the published evidence on the epidemiology of GD. MEDLINE, EMBASE, CENTRAL, and 'grey' literature sources published in English between January 1990 and March 2015 were searched to identify relevant publications.

RESULTS

In total, 188 full-text articles were reviewed and findings from 49 studies are summarized herein. The standardized birth incidence of GD in the general population varied from 0.39 to 5.80 per 100 000, and prevalence ranged from 0.70 to 1.75 per 100 000, respectively. Time from onset of GD symptoms to clinical diagnosis was highly variable, with median delays of up to 7 years reported.

DISCUSSION

The incidence and prevalence of GD is substantially higher among the Ashkenazi Jewish population than the general population. Limited epidemiologic information was available from Latin America, Africa, Asia, and developed nations such as the United States, Germany, and the United Kingdom.

CONCLUSIONS

Signs and symptoms of GD frequently mimic more common hematologic conditions resulting in missed or delayed diagnosis. Early diagnosis and prompt initiation of treatment when indicated is crucial to prevent or minimize life-altering or life-threatening liver and skeletal complications.

Responsible implementation of expanded carrier screening

This document of the European Society of Human Genetics contains recommendations regarding responsible implementation of expanded carrier screening. Carrier screening is defined here as the detection of carrier status of recessive diseases in couples or persons who do not have an a priori increased risk of being a carrier based on their or their partners' personal or family history. Expanded carrier screening offers carrier screening for multiple autosomal and X-linked recessive disorders, facilitated by new genetic testing technologies, and allows testing of individuals regardless of ancestry or geographic origin. Carrier screening aims to identify couples who have an increased risk of having an affected child in order to facilitate informed reproductive decision making. In previous decades, carrier screening was typically performed for one or few relatively common recessive disorders associated with significant morbidity, reduced life-expectancy and often because of a considerable higher carrier frequency in a specific population for certain diseases. New genetic testing technologies enable the expansion of screening to multiple conditions, genes or sequence variants. Expanded carrier screening panels that have been introduced to date have been advertised and offered to health care professionals and the public on a commercial basis. This document discusses the challenges that expanded carrier screening might pose in the context of the lessons learnt from decades of population-based carrier screening and in the context of existing screening criteria. It aims to contribute to the public and professional discussion and to arrive at better clinical and laboratory practice guidelines.

Expanded genetic screening panel for the Ashkenazi Jewish population

PURPOSE

Carrier screening programs that identify the presence of known mutations have been effective for reducing the incidence of autosomal recessive conditions in the Ashkenazi Jewish (AJ) population and other populations. Yet, these programs have not realized their full potential. Furthermore, many known autosomal recessive and dominant conditions are not screened for and the molecular basis of other conditions for which screening might be offered is unknown.

METHODS

Through literature review and annotation of full sequenced genomes from healthy individuals, we expanded the list of mutations. Mutations were identified in a sample of 128 fully sequenced AJ genomes that were filtered through clinical databases and curated manually for clinical validity and utility using the American College of Medical Genetics and Genomics scoring (ACMG) system. Other known mutations were identified through literature review.

RESULTS

A panel of 163 mutations was identified for 76 autosomal recessive, 24 autosomal dominant, and 3 X-linked disorders.

CONCLUSION

Screening for a broader range of disorders not only could further reduce the incidence of autosomal recessive disorders but also could offer the benefits of early or presymptomatic diagnosis.Genet Med 18 5, 522-528.

Proof-of-principle rapid noninvasive prenatal diagnosis of autosomal recessive founder mutations

BACKGROUND

Noninvasive prenatal testing can be used to accurately detect chromosomal aneuploidies in circulating fetal DNA; however, the necessity of parental haplotype construction is a primary drawback to noninvasive prenatal diagnosis (NIPD) of monogenic disease. Family-specific haplotype assembly is essential for accurate diagnosis of minuscule amounts of circulating cell-free fetal DNA; however, current haplotyping techniques are too time-consuming and laborious to be carried out within the limited time constraints of prenatal testing, hampering practical application of NIPD in the clinic. Here, we have addressed this pitfall and devised a universal strategy for rapid NIPD of a prevalent mutation in the Ashkenazi Jewish (AJ) population.

METHODS

Pregnant AJ couples, carrying mutation(s) in GBA, which encodes acid β-glucosidase, were recruited at the SZMC Gaucher Clinic. Targeted next-generation sequencing of GBA-flanking SNPs was performed on peripheral blood samples from each couple, relevant mutation carrier family members, and unrelated individuals who are homozygotes for an AJ founder mutation. Allele-specific haplotypes were constructed based on linkage, and a consensus Gaucher disease-associated founder mutation-flanking haplotype was fine mapped. Together, these haplotypes were used for NIPD. All test results were validated by conventional prenatal or postnatal diagnostic methods.

RESULTS

Ten parental alleles in eight unrelated fetuses were diagnosed successfully based on the noninvasive method developed in this study. The consensus mutation-flanking haplotype aided diagnosis for 6 of 9 founder mutation alleles.

CONCLUSIONS

The founder NIPD method developed and described here is rapid, economical, and readily adaptable for prenatal testing of prevalent autosomal recessive disease-causing mutations in an assortment of worldwide populations.

FUNDING

SZMC, Protalix Biotherapeutics Inc., and Centogene AG.

Do people from the Jewish community prefer ancestry-based or pan-ethnic expanded carrier screening?

Ancestry-based carrier screening in the Ashkenazi Jewish population entails screening for specific autosomal recessive founder mutations, which are rarer among the general population. As it is now technically feasible to screen for many more diseases, the question arises whether this population prefers a limited ancestry-based offer or a pan-ethnic expanded carrier screening panel that goes beyond the diseases that are frequent in their own population, and is offered regardless of ancestry. An online questionnaire was completed by 145 individuals from the Dutch Jewish community (≥18 years) between April and July 2014. In total, 64.8% were aware of the existence of ancestry-based carrier screening, and respondents were generally positive about screening. About half (53.8%) preferred pan-ethnic expanded carrier screening, whereas 42.8% preferred ancestry-based screening. Reasons for preferring pan-ethnic screening included ‘everyone has a right to be tested', ‘fear of stigmatization when offering ancestry-based panels', and ‘difficulties with identifying risk owing to mixed backgrounds'. ‘Preventing high healthcare costs' was the most important reason against pan-ethnic carrier screening among those in favor of an ancestry-based panel. In conclusion, these findings show that people from the Dutch Jewish community have a positive attitude regarding carrier screening in their community for a wide range of diseases. As costs of expanded carrier screening panels are most likely to drop in the near future, it is expected that these panels will receive more support in the future.

High-throughput carrier screening using TaqMan allelic discrimination

Members of the Ashkenazi Jewish community are at an increased risk for inheritance of numerous genetic diseases such that carrier screening is medically recommended. This paper describes the development and evaluation of 30 TaqMan allelic discrimination qPCR assays for 29 mutations on 2 different high-throughput platforms. Four of these mutations are in the GBA gene and are successfully examined using short amplicons due to the qualitative nature of TaqMan allelic discrimination. Two systems were tested for their reliability (call rate) and consistency with previous diagnoses (diagnostic accuracy) indicating a call rate of 99.04% and a diagnostic accuracy of 100% (+/−0.00%) from one platform, and a call rate of 94.66% and a diagnostic accuracy of 93.35% (+/−0.29%) from a second for 9,216 genotypes. Results for mutations tested at the expected carrier frequency indicated a call rate of 97.87% and a diagnostic accuracy of 99.96% (+/−0.05%). This study demonstrated the ability of a high throughput qPCR methodology to accurately and reliably genotype 29 mutations in parallel. The universally applicable nature of this technology provides an opportunity to increase the number of mutations that can be screened simultaneously, and reduce the cost and turnaround time for accommodating newly identified and clinically relevant mutations.

Genetic counseling services and training of genetic counselors in Israel: an overview

Genetic counseling services have existed in Israel since 1964 and are available in almost all the major hospitals. Given the socialized healthcare system and small country size, genetic services are generally accessible and often free. The existence of founder mutations in various communities in Israel makes genetic testing easier to perform. Yet, the ethnic, cultural and religious diversity of the population has major implications on the design of the screening programs and the use of genetic services. The Israeli Association of Genetic Counselors (IAGC) was established in 2008 and had existed informally since 1989. There are two Master level genetic counseling training programs (6 students/class, 2 year program): Hebrew University-Hadassah Medical School (established in 1997) and the Technion (established in 2009). Genetic counselors' clinical training is largely observational and 2 years of supervised counseling sessions post degree are required for board exam eligibility. Genetic counselors are licensed and lead counseling sessions individually, but currently must work under medical geneticist supervision. This is the first article to summarize the history and training of Master level genetic counselors in Israel. Genetic services, coverage and regulations are also described.

The link between the GBA gene and parkinsonism

Mutations in the glucocerebrosidase (GBA) gene, which encodes the lysosomal enzyme that is deficient in Gaucher's disease, are important and common risk factors for Parkinson's disease and related disorders. This association was first recognised in the clinic, where parkinsonism was noted, albeit rarely, in patients with Gaucher's disease and more frequently in relatives who were obligate carriers. Subsequently, findings from large studies showed that patients with Parkinson's disease and associated Lewy body disorders had an increased frequency of GBA mutations when compared with control individuals. Patients with GBA-associated parkinsonism exhibit varying parkinsonian phenotypes but tend to have an earlier age of onset and more associated cognitive changes than patients with parkinsonism without GBA mutations. Hypotheses proposed to explain this association include a gain-of-function due to mutations in glucocerebrosidase that promotes α-synuclein aggregation; substrate accumulation due to enzymatic loss-of-function, which affects α-synuclein processing and clearance; and a bidirectional feedback loop. Identification of the pathological mechanisms underlying GBA-associated parkinsonism will improve our understanding of the genetics, pathophysiology, and treatment for both rare and common neurological diseases.

The ethics of screening for disease

Screening can identify individuals at increased risk of or in the early stage of a disease at a time when intervention can reduce the risk of morbidity and mortality. There are many ethical issues that have arisen as a result of screening. These can relate to the process of screening in general or to specific screening programs. Examples of the former include issues related to consent for screening, the utility of the screening tests employed and issues of funding of screening programs and equity of access to screening. Ethical issues related to three specific areas of screening are explored in more detail: reproductive screening, screening for disease with onset in adulthood and newborn screening. It is critical that ethical issues are considered in planning screening programs so as to ensure that the main focus of screening, preventing morbidity, is maximised. There are many lessons to be learnt from the many screening programs that have been conducted worldwide. No doubt new ethical issues will arise as new technologies and new treatments are developed, enabling screening for more conditions at lower relative costs.

Adult Gaucher disease in southern Tunisia: report of three cases

Background

Gaucher disease (GD) is the most frequent lysosomal storage disorder; type 1 is by far the most common form. It is characterized by variability in age of onset, clinical signs and progression. It is usually diagnosed in the first or second decade of life with the appearance of bone pains, splenomegaly and thrombocytopenia, but the disease may be diagnosed at any age between 1 and 73 years. In the present study, we report 3 cases with late onset of GD in whom the disease was a surprise finding including one patient with Parkinson disease. This late onset is described as an adult form of Gaucher disease.

Findings

Molecular investigation showed mutational homogeneity in Tunisian adult patients suffering from GD. Indeed, all patients carry the p.N370S mutation: two patients at a homozygous state and one patient at compound heterozygous state.

Conclusion

The p.N370S mutation presents a large variability in the onset of the disease and its clinical manifestation supporting the view that GD should be considered as a continuum phenotype rather than a predefined classification.

Preconception care and genetic risk: ethical issues

Preconception care to address genetic risks in reproduction may be offered either individually to couples with a known or suspected increased risk of having a child with a genetic disorder, or systematically to couples or individuals of reproductive age. The identification of couples at risk of transmitting a (serious) genetic disorder allows those couples to refrain from having children or to adapt their reproductive plans (using prenatal or preimplantation diagnosis, donor gametes, or adoption). Ethical issues concern the possible objectives of providing these options through preconception genetic counseling or screening, objections to abortion and embryo-selection, concerns about eugenics and medicalization, and issues arising in the professional–client relationship and/or in the light of the normative framework for population screening. Although enhancing reproductive autonomy rather than prevention should be regarded as the primary aim of preconception care for genetic risks, directive counseling may well be acceptable in exceptional cases, and prevention in the sense of avoiding serious suffering may be an appropriate objective of specific community-based preconception screening programmes. The seemingly unavoidable prospect of comprehensive preconception screening raises further ethical issues.

How I treat Gaucher disease

This review presents a cohesive approach to treating patients with Gaucher disease. The spectrum of the clinical presentation of the disease is broad, yet heretofore there was only one disease-specific treatment. In the past 2 years, a global shortage of this product has resulted in reassessment of the “one enzyme–one disease–one therapy” mantra. It has also showcased the multiple levels that engage the patient, the treating physician, and the third-party insurer in providing adequate treatment to all symptomatic patients. The key points summarizing the way I manage my patients include accurate enzymatic diagnosis with mutation analysis (for some prognostication and better carrier detection in the family), a detailed follow-up every 6-12 months (with an option to see consultants and attention to comorbidities), and initiation of enzyme replacement therapy according to symptoms or deterioration in clinically significant features or both. I do not treat patients with very mild disease, but I consider presymptomatic therapy for patients at risk, including young women with poor obstetric history. I prefer the minimal-effective dose rather than the maximally tolerated dose, and when the difference between high-dose and lower-dose regimens is (merely statistically significant but) clinically meaningless, minimizing the burden on society by advocating less-expensive treatments is ethically justified.

Preconceptional genetic carrier testing and the commercial offer directly-to-consumers

Recently, a number of commercial companies are offering preconceptional carrier tests directly-to-consumers. This offer raises a number of concerns and issues above and beyond those encountered with preconceptional tests offered within the traditional health care setting. In order to bring some of these issues to light and to initiate dialogue on this topic, this article discusses the following issues: the current offer of preconceptional carrier tests (until the end of 2010) through online commercial companies; the implications for the informed consent procedure and the need for good information; the need for medical supervision and follow-up; and the appropriate use of existing resources. The article concludes with some reflections about the potential sustainability of the offer of preconceptional carrier tests directly-to-consumers.

Carrier screening for spinal muscular atrophy (SMA) in 107,611 pregnant women during the period 2005-2009: a prospective population-based cohort study

Background

Spinal muscular atrophy (SMA) is the most common neuromuscular autosomal recessive disorder. The American College of Medical Genetics has recently recommended routine carrier screening for SMA because of the high carrier frequency (1 in 25–50) as well as the severity of that genetic disease. Large studies are needed to determine the feasibility, benefits, and costs of such a program.

Methods and Findings

This is a prospective population-based cohort study of 107,611 pregnant women from 25 counties in Taiwan conducted during the period January 2005 to June 2009. A three-stage screening program was used: (1) pregnant women were tested for SMA heterozygosity; (2) if the mother was determined to be heterozygous for SMA (carrier status), the paternal partner was then tested; (3) if both partners were SMA carriers, prenatal diagnostic testing was performed. During the study period, a total of 2,262 SMA carriers with one copy of the SMN1 gene were identified among the 107,611 pregnant women that were screened. The carrier rate was approximately 1 in 48 (2.10%). The negative predictive value of DHPLC coupled with MLPA was 99.87%. The combined method could detect approximately 94% of carriers because most of the cases resulted from a common single deletion event. In addition, 2,038 spouses were determined to be SMA carriers. Among those individuals, 47 couples were determined to be at high risk for having offspring with SMA. Prenatal diagnostic testing was performed in 43 pregnant women (91.49%) and SMA was diagnosed in 12 (27.91%) fetuses. The prevalence of SMA in our population was 1 in 8,968.

Conclusion

The main benefit of SMA carrier screening is to reduce the burden associated with giving birth to an affected child. In this study, we determined the carrier frequency and genetic risk and provided carrier couples with genetic services, knowledge, and genetic counseling.

Experience with carrier screening and prenatal diagnosis for 16 Ashkenazi Jewish genetic diseases

The success of prenatal carrier screening as a disease prevention strategy in the Ashkenazi Jewish (AJ) population has driven the expansion of screening panels as disease-causing founder mutations have been identified. However, the carrier frequencies of many of these mutations have not been reported in large AJ cohorts. We determined the carrier frequencies of over 100 mutations for 16 recessive disorders in the New York metropolitan area AJ population. Among the 100% AJ-descended individuals, screening for 16 disorders resulted in ∼1 in 3.3 being a carrier for one disease and ∼1 in 24 for two diseases. The carrier frequencies ranged from 0.066 (1 in 15.2; Gaucher disease) to 0.006 (1 in 168; nemaline myopathy), which averaged ∼15% higher than those for all screenees. Importantly, over 95% of screenees chose to be screened for all possible AJ diseases, including disorders with lower carrier frequencies and/or detectability. Carrier screening also identified rare individuals homozygous for disease-causing mutations who had previously unrecognized clinical manifestations. Additionally, prenatal testing results and experience for all 16 disorders (n = 574) are reported. Together, these data indicate the general acceptance, carrier frequencies, and prenatal testing results for an expanded panel of 16 diseases in the AJ population.

Type 1 Gaucher disease: significant disease manifestations in "asymptomatic" homozygotes

BACKGROUND

Type 1 Gaucher disease (GD), an autosomal recessive lysosomal storage disease, is most prevalent in the Ashkenazi Jewish (AJ) population. Experts have suggested that up to two-thirds of AJ homozygotes for the common mutation (N370S) are asymptomatic throughout life and never come to medical attention. However, there are no systematic studies of N370S homozygotes to support this presumption.

METHODS

Prenatal carrier screening of 8069 AJ adults for 6 common GD mutations was performed. Gaucher disease manifestations in 37 previously unrecognized homozygotes were assessed by clinical, laboratory, and imaging studies.

RESULTS

Among the 8069 AJ screenees, 524 GD carriers (1:15) and 9 previously unrecognized GD homozygotes (1:897) were identified, consistent with the rate expected (1:949; P > .99). Six of these homozygotes and 31 AJ GD homozygotes identified by other prenatal carrier screening programs in the New York City metropolitan area were evaluated (age range of the homozygotes, 17-40 years). Of these, 84% were N370S homozygotes, others being heteroallelic for N370S and V394L, L444P, or R496H mutations. Notably, 65% reported no GD medical complaints. However, 49% had anemia and/or thrombocytopenia. Among the 29 who had imaging studies, 97% had mild to moderate splenomegaly and 55% had hepatomegaly; skeletal imaging revealed marrow infiltration (100%), Erlenmeyer flask deformities (43%), lucencies (22%), and bone infarcts (14%). Dual energy X-ray absorptiometry studies of 25 homozygotes found 60% with osteopenia or osteoporosis.

CONCLUSION

Contrary to previous discussions, almost all asymptomatic GD homozygotes serendipitously diagnosed by prenatal carrier screening had disease manifestations and should be followed for disease progression and institution of appropriate medical treatment.

Malaria, mummies, mutations: Tutankhamun's archaeological autopsy

The cause of death of the Egyptian pharoah Tutankhamun has now for decades been matter of speculation and various hypotheses. A recent article in the Journal of the American Medical Association (JAMA) provided new evidence and suggested malaria, together with Köhler’s disease, as the most probable cause of death of the boy king. We are sceptical towards this elucidation of the cause of death of King Tut and discuss alternative and differential diagnoses, among them, in particular, sickle cell disease and Gauche’s disease.

A universal carrier test for the long tail of Mendelian disease

Mendelian disorders are individually rare but collectively common, forming a 'long tail' of genetic disease. A single highly accurate assay for this long tail would allow the scaling up of the Jewish community's successful campaign of population screening for Tay-Sachs disease to the general population, thereby improving millions of lives, greatly benefiting minority health and saving billions of dollars. This need has been addressed by designing a universal carrier test: a non-invasive, saliva-based assay for more than 100 Mendelian diseases across all major population groups. The test has been exhaustively validated with a median of 147 positive and 525 negative samples per variant, demonstrating a multiplex assay whose performance compares favourably with the previous standard of care, namely blood-based single-gene carrier tests. Because the test represents a dramatic reduction in the cost and complexity of large-scale population screening, an end to many preventable genetic diseases is now in sight. Moreover, given that the assay is inexpensive and requires only a saliva sample, it is now increasingly feasible to make carrier testing a routine part of preconception care.

Preimplantation genetic diagnosis (PGD) for a treatable disorder: Gaucher disease type 1 as a model

BACKGROUND

Preimplantation genetic diagnosis (PGD) is a technique that enables identification of unaffected embryos prior to in vitro fertilization (IVF) transfer in couples at risk for a Mendelian disorder. Most cases involve severe genetic diseases with neurological features and/or major malformations. We present two couples in which PGD was performed for prevention of type 1 Gaucher disease, a non-neuronopathic, non-lethal disorder.

MATERIALS AND METHODS

We developed a multiplex fluorescent PCR protocol, simultaneously amplifying the familial mutations and eight closely spaced, highly polymorphic informative microsatellite markers surrounding the gene, to be used for PGD analysis.

RESULTS

Couple #1 mother was homozygous for the N370S mutation and the father carried the 84GG mutation; their first daughter receives specific Gaucher therapy. One PGD cycle resulted in seven embryos of which four had the paternal wild type allele; two were transferred resulting in a healthy baby boy born at term. Couple #2, each a carrier (N370S and R359Q), whose first-born child had died (age 5years) of Gaucher disease, underwent 7 PGD cycles. Only one cycle resulted in a clinical pregnancy but a miscarriage was followed at 10weeks.

CONCLUSIONS

PGD is an effective and accurate method for preventing Gaucher disease type I in carrier couples. Since this disease is treatable, special ethical considerations and careful selection of couples should be performed.

The female Gaucher patient: the impact of enzyme replacement therapy around key reproductive events (menstruation, pregnancy and menopause)

BACKGROUND

The principal manifestations of type 1 Gaucher disease (GD) (increased risk of bleeding, anaemia, splenomegaly, hepatomegaly and bone disease) are likely to affect females during reproductive events such as menarche and menstruation; fertility, pregnancy, parity, delivery and lactation; and menopause. In order to determine the optimal management of female Gaucher patients based on available data, we examine reproductive events and GD in untreated and alglucerase and/or imiglucerase-treated females.

METHODS

A panel of international clinicians experienced in the management of GD reviewed and presented evidence from peer-reviewed literature, a pharmacovigilance database on imiglucerase, and their own clinical experience to support discussions and recommendations. Nine panel members completed a 130-item-questionnaire on the outcomes of the management of female patients in their clinical practice. Results, covering menarche (137 females), menstruation (261 reports), fertility (295 females), pregnancy (416 pregnancies in 247 women) and menopause (45 women) were analysed. Data from a recent Canadian survey on 50 patients with 39 pregnancies, the imiglucerase pharmacovigilance database (100 pregnancies), and relevant literature (56 items covering 398 pregnancies in 205 women) were also reviewed.

KEY RESULTS

Menarche: May be delayed in girls with GD. Menorrhagia: Appears to be more common in GD than in the non-Gaucher population and may be ameliorated by alglucerase and/or imiglucerase treatment (menorrhagia in 67/133 (50.4%) untreated females compared with 37/128 (28.9%) treated; Mann-Whitney U test: p=0.001). Fertility: There is no evidence of decreased fertility in GD. Pregnancy: Pregnancy in GD may be complicated by haematological disease, organomegaly and bone involvement. GD diagnosis occurs frequently during pregnancy. Questionnaire results demonstrate: a reduced risk of spontaneous abortion in women treated with alglucerase and/or imiglucerase (untreated: 26/189 (13.8%); treated 1/58 (1.7%) chi(2)p=0.010); reduced risk of Gaucher-related complications during delivery (untreated 43/109 (39.4%); treated 3/46 (6.5%) chi(2)p<0.0005): and a reduced risk of Gaucher-related complications during the post partum period (untreated 15/71 (21.1%); treated 3/43 (7%) chi(2)p=0.014). There is no evidence to date of any untoward effect of alglucerase and/or imiglucerase on the fetus, or on infants breast fed by mothers receiving alglucerase and/or imiglucerase. Menopause: The impact of GD on menopause requires further study especially in relation to bone pathology.

CONCLUSIONS

On the basis of this review, GD may have an impact on reproductive events in affected women. Enzyme therapy may have benefits in reducing menorrhagia, spontaneous abortions and complications associated with delivery and the postpartum period.