Characterization of Classical and Nonclassical Fabry Disease: A Multicenter Study

Disrupted synaptic gene expression in Fabry disease: Findings from RNA sequencing

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by a deficiency in the enzyme α-galactosidase A. This defect leads to the progressive accumulation of glycosphingolipids, resulting in kidney, heart, and nervous system damage, which contributes to significant morbidity and mortality. Early diagnosis is essential to prevent irreversible damage and optimize treatment strategies. Recent research aims to provide a better understanding of FD pathophysiology to improve management approaches. This study is an international, multicenter, cross-sectional analysis that used RNA sequencing (RNA-seq) to compare blood samples from 50 FD patients and 50 age- and sex-matched healthy controls. The objective was to identify gene expression patterns and investigate secondary cellular pathways affected by lysosomal dysfunction. Among the more than 400 differentially expressed genes detected, 207 were protein-coding genes, most of which were overexpressed in the FD cohort. Functional enrichment analysis highlighted processes related to synaptic function, specifically concerning chemical synaptic transmission and membrane potential regulation. Identified genes included those related to voltage-gated ion channels, neurotransmitter receptors, cell adhesion molecules, scaffold proteins, and proteins associated with synaptic vesicles and neurotrophic signaling, all linked to lipid rafts. Notable identified genes included those encoding voltage-gated potassium channel genes (KCNQ2, KCNQ3, KCNMA1) and ionotropic receptor genes involved in glutamatergic (GRIN2A, GRIN2B) and GABAergic systems (GABRA4, GABRB1, GABRG2, GABRQ). These findings suggest that lysosomal dysfunction contributes to synaptic defects in FD, paving the way for further research into the role of synaptic pathology and lipid rafts in the underlying pathogenesis and clinical outcomes in FD.

Two decades of experience of the Fabry Outcome Survey provides further confirmation of the long-term effectiveness of agalsidase alfa enzyme replacement therapy

Background

Analyses of up to 20 years of data from the Fabry Outcome Survey (FOS) assessed the long-term effectiveness of agalsidase alfa enzyme replacement therapy.

Methods

The impact of agalsidase alfa treatment on renal, cardiac, morbidity, and mortality outcomes in FOS was compared with untreated external Fabry disease (FD) cohorts.

Results

A total of 2171 FOS patients (1014 men, 919 women, 163 boys, 75 girls) received agalsidase alfa (median [range] duration of treatment: 5.38 [0.0-20.8] years). Annual rates of decline in estimated glomerular filtration rate improved in treated patients versus untreated external cohorts regardless of sex or baseline urinary protein levels. Annual left ventricular mass index rates were stable in treated patients regardless of sex or baseline left ventricular hypertrophy status, and better than in untreated external cohorts. The mean age at which 50 % of patients had their first composite morbidity event was later in the agalsidase-alfa-treated population than in the untreated external cohort (51.7 vs 41 years [males]; 60.8 vs 53 years [females]). After 24 months of treatment, the probability of a composite morbidity event was ∼34 % in treated patients and ∼ 45 % in untreated patients. Treated patients were older at death than untreated patients (mean [range]: 61.7 [26.2-87.6] vs 50.3 [34.5-70.1] years). The mean age at which 50 % of male patients were still alive was higher in treated patients than in untreated external cohorts (75.5 vs 60.0 years).

Conclusions

Long-term treatment with agalsidase alfa may provide renal, cardiac, and overall survival protection in FD.

Fabry disease in the haemodialysis population: outcome of a UK screening study (SoFAH)

BACKGROUND AND HYPOTHESIS

Fabry disease (FD) is an X-linked inherited disorder with an estimated prevalence among the end-stage kidney disease (ESKD) population of 0.3% in men and 0.1% in women [1]. Due to its non-specific manifestations, FD (especially the later-onset variant) is often underdiagnosed [2]. We aimed to estimate its prevalence in a large haemodialysis (HD) population in the UK.

METHODS

This is a cross-sectional, multicentre study of eight renal centres in the UK. All male participants were tested via dried blood spot alpha-galactosidase A (AG) enzyme and globotriaosylsphingosine (Lyso-Gb3) assays. If either the AG (≤ 2.8 µmol/L/H) or Lyso-Gb3 (≥ 3.5 ng/mL) level was abnormal, genetic testing for GLA variant was performed. All females had AG, Lyso-GB3 and genetic tests.

RESULTS

In total, 1325 consented to participate in the study. The mean age of the participants was 64 (SD 15) years, 67% were male, 64% were of white ethnicity, the duration of dialysis was 32 (IQR 56) months, and 32% underwent renal biopsy. Diabetic nephropathy (28%) was the most common cause of ESKD, whereas 21% had an unknown aetiology. A total of 1,295 had both AG and Lyso-Gb3 tests, whereas 573 had GLA genetic tests. Among the 14% (n = 186) with an AG level ≤ 2.8 µmol/L/H, 48 were female and 138 were male, all of whom had Lyso-Gb3 < 3.5 ng/mL. Only 3 (0.2%) had abnormal Lyso-Gb3 but all had normal AG and negative genetic tests. Two females were found to have likely benign, non-pathogenic GLA variants: heterozygous c.937G > T (p.(Asp313Tyr) and heterozygous c.1102G > A (p.(Ala368Thr)).

CONCLUSIONS

Despite the implementation of stringent screening criteria, we did not identify any new confirmed cases of Fabry disease in this large UK haemodialysis population.

Correlation of enzyme activities and genotype with clinical manifestations in Chinese patients of different sexes with classical and late-onset Fabry disease

Fabry disease, a rare genetic disorder affecting multiple organs, has understudied correlations among enzyme activity, genotype, and clinical manifestations in patients of different sexes with classical and late-onset phenotypes. In this study, clinical data, α-Gal A activity, and GLA gene test results of 311 patients, who were categorized by classical and late-onset phenotypes, ⩽5% and > 5% of the normal mean value of enzyme activity, and truncated and nontruncated mutation groups, were collected. The common clinical manifestations of Fabry disease included acroparesthesia, hypohidrosis/anhidrosis, neuropsychiatric system, and renal and cardiovascular involvement. Multiorgan involvement was higher in males and classical phenotype patients. In both sexes, classical patients commonly presented with acroparesthesia and multiorgan involvement, whereas late-onset patients showed renal, neuropsychiatric, and cardiovascular involvement. Male and classical patients had lower enzyme activity than female and late-onset patients, respectively. Classical males with enzyme activity of ⩽5% of the normal mean level showed higher multiorgan involvement frequency than those with enzyme activity of > 5%, whereas no significant difference was observed among females. Ninety-five gene mutation sites were detected, with significant phenotype heterogeneity in patients with the same mutation. No significant difference in enzyme activity or clinical manifestations was observed between truncated and nontruncated mutations. Overall, male patients with Fabry disease, regardless of classical or late-onset phenotype, have a higher frequency of multiple-organ involvement and lower α-Gal A activity than female patients. α-Gal A activity was closely correlated with clinical symptoms in males but weakly correlated with clinical manifestations in females. The clinical manifestations of patients with the same mutation are heterogeneous, and the correlation between gene mutation and enzyme activity or clinical manifestation is weak.

Role of Biomarkers in Diagnosing Disease, Assessing the Severity and Progression of Disease, and Evaluating the Efficacy of Therapies

This paper reviews biomarkers in lysosomal disease according to their categories and definitions. There are numerous biomarkers in lysosomal diseases. Some are disease or organ-specific, but most are not. Organ-specific biomarkers are especially useful, but most biomarkers help with diagnosis, assessing disease severity, prognosis, and pharmacodynamic response. There are as yet no truly validated biomarkers in lysosomal diseases by the Prentice, Fleming, and DeMets criteria. None so far can serve as surrogate endpoints in clinical trials, or as substitutes for clinically meaningful endpoints that evaluate how patients feel, function, or survive. The US Food and Drug Administration has thus far used surrogate biomarkers to license therapy only for 3 lysosomal diseases-Gaucher disease, Fabry disease, and lysosomal lipase deficiency. The paucity of surrogate biomarkers reflects success in using clinically important endpoints for the licensing of therapies for Pompe disease, mucopolysaccharidosis IVA, VI, and VII, Niemann-Pick type C, and CLN2. In conclusion, biomarkers in lysosomal diseases are best used for diagnosis, patient categorization, pharmacodynamic response, and sometimes for patient prognosis and risk. Thus far, they have been less useful as surrogate biomarkers in pivotal clinical trials.

Enhancing Fabry disease screening and diagnostic efficiency: Integration of enzyme, biomarker, and next-generation sequencing testing

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by a deficiency of alpha-galactosidase A (α-Gal A) due to pathogenic variants of the GLA gene. This study reports findings from data collected through The Lantern Project, including results from α-Gal A enzyme activity and globotriaosylsphingosine (lyso-Gb3) biomarker assays from dried blood spots, as well as next-generation sequencing (NGS). A total of 513 enzyme tests, 284 lyso-Gb3 tests, and 994 NGS tests were conducted on 1380 individuals (708 female, 661 male, 11 sex unknown) with clinical suspicion, or family history or abnormal newborn screening (NBS) results who participated in the project from December 2018-April 2023. Among these individuals, 21 % (103 male and 2 sex unknown) had abnormal α-Gal A levels (range 0.054-1.069 μM/h, normal level ≥ 1.10 μM/h), and 70 % (79 female, 115 male and 2 sex unknown) had elevated lyso-Gb3 levels (range 1.12-130.56 ng/mL, normal level ≤ 1.11 ng/mL). A total of 137 different reportable variants have been identified in this cohort including novel variants c.[351T>G;361G>C] (p.I117M;A121P), c.370-558_370-1del, c.548del, and c.1165C>T (p.P389S). All female patients with loss-of-function (LOF) variants and biomarker results were found to have elevated lyso-Gb3 levels. In contrast to those with LOF variants, females with missense GLA variants had various lyso-Gb3 results. Pathogenic (P)/likely pathogenic (LP) missense variants [including c.1087C>T (p.R363C), c.1088G>A (p.R363H), c.593T>C (p.I198T), c.644A>G (p.N215S), c.335G>A (p.R112H), c.337T>C (p.F113L), and c.835C>G (p.Q279E)] were identified in 16 female patients with normal lyso-Gb3 levels. These findings suggest that the use of lyso-Gb3 testing without GLA sequencing may result in missed diagnosis in some female patients with FD missense variants. Different biochemical and DNA variant profiles have been observed between NBS and non-NBS male patients. Among the non-NBS males, both enzyme and biomarker results correlate with age at the time of testing, which appear to be an approximated indicator for age of onset and disease severity. Among all the NBS males with both enzyme and lyso-Gb3 results, abnormal α-Gal A levels were found in all having P/LP variants except for the 11 who had c.427G>A (p.A143T) or c.870G>C (p.M290I), while normal lyso-Gb3 results have been found in many males with various P/LP variants - though it should of course be noted that lyso-Gb3 levels may increase over time. Our observation in NBS male patients may suggest that the enzyme test has a higher sensitivity, while lyso-Gb3 test has a higher specificity, and when combined with DNA test results, can provide a more comprehensive and reliable result. This manuscript presents the largest-to-date, comprehensive, multi-testing Fabry cohort with demographic information and biochemical phenotypes from a single clinical laboratory. The results from this dataset demonstrate that the integration of enzyme, biomarker, and NGS testing can enhance screening/diagnostic efficiency for FD, particularly for female patients.

Safety and efficacy of migalastat in adolescent patients with Fabry disease: Results from ASPIRE, a phase 3b, open-label, single-arm, 12-month clinical trial, and its open-label extension

Fabry disease (FD) is a progressive, multisystemic, X-linked lysosomal disorder caused by reduced or absent α-galactosidase A activity due to galactosidase alpha (GLA) gene variants. Although clinical manifestations of FD often appear in childhood, approved treatments for the management of FD in children and adolescents are limited. ASPIRE (NCT03500094) was a phase 3b, two-stage, open-label, multicenter study evaluating the safety, pharmacokinetics, and efficacy of migalastat in adolescents 12 to <18 years, ≥ 45 kg with FD and amenable GLA variants. Long-term outcomes were evaluated in the ongoing open-label extension (OLE) study (NCT04049760). Pharmacokinetic results (a primary objective of ASPIRE) were reported previously. Here, we report safety, efficacy, pharmacodynamic, and patient-reported outcome measures in adolescents treated with migalastat for up to 48 months across ASPIRE and the subsequent OLE. Outcome measures included treatment-emergent adverse events, estimated glomerular filtration rate, left ventricular mass index, plasma globotriaosylsphingosine (lyso-Gb3) levels, the Fabry-specific Pediatric Health and Pain Questionnaire (FPHPQ), and the Pediatric Quality of Life Inventory™. Overall, 21 patients (52.4 % female) received at least one dose of migalastat in ASPIRE, 11 of whom were enzyme replacement therapy experienced. Mean age at study entry was 14.7 years. Treatment with migalastat was well tolerated in this adolescent population with no new or unexpected safety findings observed. Renal and cardiac measures remained within the normal range for adolescent patients throughout ASPIRE and the OLE with no meaningful changes observed with migalastat treatment. Plasma lyso-Gb3 levels were stable. Pain related to heat or exertion (as measured by FPHPQ) improved with migalastat treatment, and other patient-reported measures of pain, gastrointestinal symptoms, and quality of life remained stable. These data show a benefit of long-term migalastat treatment in this adolescent patient population with amenable GLA variants.

The use and performance of lyso-Gb3 for the diagnosis and monitoring of Fabry disease: A systematic literature review

BACKGROUND

Fabry disease (FD) is a rare, X-linked lysosomal storage disorder in which a lack of alpha-galactosidase (α-Gal A) enzyme activity leads to intracellular accumulation of deacylated globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3), and their analogs. Lyso-Gb3, present in the blood and urine of affected patients, has been extensively investigated as a biomarker for FD. This systematic literature review (SLR) aimed to comprehensively assess the use of lyso-Gb3 as a biomarker for screening, monitoring, and diagnosis of FD in both real-world and clinical trial settings.

METHODS

An SLR was performed to identify the following outcomes in adult and pediatric patients with FD: lyso-Gb3 testing patterns, lyso-Gb3 levels in subpopulations, performance and accuracy of lyso-Gb3 testing for diagnosis, and lyso-Gb3 testing for monitoring of disease progression or treatment efficacy/effectiveness. Interventional and non-interventional studies published between 1 January 2017 and 3 November 2022 were included. Searches were primarily conducted in MEDLINE and Embase; pragmatic or hand searches were also performed. The methodological quality of included full-text studies was assessed using validated appraisal tools. Extracted data were synthesized qualitatively.

RESULTS

The SLR included 83 eligible publications, comprising 71 observational studies and 12 clinical trials. Differences in lyso-Gb3 levels were identified across subpopulations, with several studies reporting higher levels in males versus females. Lyso-Gb3 demonstrated good diagnostic performance in newborns and high-risk patients when used in combination with other markers (α-Gal A activity or GLA variants) but failed to diagnose females with late-onset FD. Reliability and stability across different methods used to measure lyso-Gb3 was high, with a coefficient of variation <10 % for inter- and intra-assay measurements. Several studies identified moderate to strong correlation between plasma lyso-Gb3 levels and cardiac measures, but association with renal measures needs further investigation.

CONCLUSIONS

Lyso-Gb3 testing demonstrated accuracy in screening, diagnosis, and monitoring of FD in certain subpopulations, particularly males, but considering its lower sensitivity in late-onset female patients, it should be used in conjunction with other tools. Given the reliability of the test, it can be considered a feasible method for monitoring disease progression in FD in individual patients. Several gaps in the literature were identified, warranting further investigation.

REGISTRATION

PROSPERO (CRD42022375141).

Exome sequencing of a Portuguese cohort of early-onset Alzheimer's disease implicates the X-linked lysosomal gene GLA

Cerebrovascular disease is a common comorbidity in patients with Alzheimer's disease (AD) and other dementias. Accumulating evidence suggests that dysfunction of the cerebral vasculature and AD neuropathology interact in multiple ways. Additionally, common variants in COL4A1 and rare variants in HTRA1, NOTCH3, COL4A1, and CST3 have been associated with AD pathogenesis. We aimed to search for rare genetic variants in genes associated with monogenic small vessel disease in a cohort of Portuguese early-onset AD patients. We performed whole-exome sequencing in 104 thoroughly studied patients with early-onset AD who lacked known pathogenic variants in the genes associated with AD or frontotemporal dementia. We searched for rare (minor allele frequency < 0.001) non-synonymous variants in genes associated with small vessel disease: NOTCH3, HTRA1, COL4A1, COL4A2, CSTA, GLA, and TREX1. We identified 12 rare variants in 18 patients (17.3% of the cohort). Three male AD patients carried a pathogenic GLA variant (p.Arg118Cys). One of these patients had a definite neuropathological study, confirming the diagnosis of AD and showing concomitant Fabry pathology in CA1-CA4 and the subiculum. We also found several rare variants in other genes associated with cSVD (NOTCH3, COL4A2 and HTRA1), corroborating previous studies and providing further support for the possibility that cSVD genes may play a role in AD pathogenesis. The presence of the same GLA variant in 3 early-onset AD patients, with no other genetic cause for the disease, together with the colocalization of Fabry disease pathology in areas relevant for AD pathogenesis, suggest GLA may have a role in its pathophysiology, possibly parallel to that of GBA in Parkinson's disease, meriting further studies.

Misprocessing of α -Galactosidase A, Endoplasmic Reticulum Stress, and the Unfolded Protein Response

Key Points

The clinical significance of a number of missense variants of α -galactosidase A is often ambiguous. Defective proteostasis of some missense α -galactosidase A variants induced chronic endoplasmic reticulum stress and the unfolded protein response. Endoplasmic reticulum stress and the unfolded protein response may explain clinical manifestations of non-classic Fabry disease.

Background

Classic Fabry disease is caused by GLA mutations that result in loss of enzymatic activity of α -galactosidase A, lysosomal storage of globotriaosylceramide, and a resulting multisystemic disease. In non-classic Fabry disease, patients have some preserved α -galactosidase A activity and a milder disease course. Heterozygous female patients may also be affected. While Fabry disease pathogenesis has been mostly attributed to catalytic deficiency of mutated α -galactosidase A, lysosomal storage, and impairment of lysosomal functions, other pathogenic factors may contribute, especially in nonclassic Fabry disease.

Methods

We characterized the genetic, clinical, biochemical, molecular, cellular, and organ pathology correlates of the p.L394P α -galactosidase A variant that was identified initially in six individuals with kidney failure by the Czech national screening program for Fabry disease and by further screening in an additional 24 family members.

Results

Clinical findings in affected male patients revealed a milder clinical course, with approximately 15% residual α -galactosidase A activity with normal plasma lyso-globotriaosylceramide levels and abnormally low ratio of these values. None of the four available kidney biopsies showed lysosomal storage. Laboratory investigations documented intracellular retention of mutated α -galactosidase A with resulting endoplasmic reticulum stress and the unfolded protein response, which were alleviated with BRD4780, a small molecule clearing misfolded proteins from the early secretory compartment. We observed similar findings of endoplasmic reticulum stress and unfolded protein response in five kidney biopsies with several other classic and non-classic Fabry disease missense α -galactosidase A variants.

Conclusions

We identified defective proteostasis of mutated α -galactosidase A resulting in chronic endoplasmic reticulum stress and unfolded protein response of α -galactosidase A expressing cells as a contributor to Fabry disease pathogenesis.

Long-term enzyme replacement therapy in Fabry patients protects against oxidative and inflammatory process

Fabry disease (FD) is an X-linked recessive lysosomal storage disorder, characterized by a deficiency of α-galactosidase, which causes the progressive accumulation of glycosphingolipids, especially globotriaosylsphingosine (Gb3), in lysosomes across multiple organs. Substrate deposition, associated with tissue damage in FD, also contributes to the emergence of a pro-inflammatory state presented by some patients. We investigated pro- and anti-inflammatory cytokines, and the expression of inflammation-associated genes in treated FD patients, as well as oxidative parameters. We found a decrease in the production of cytokines IL-1β, IL-6, IL-10, and TNF-α in male FD patients and a normalization of redox status in male and female FD patients, once the levels of protein, lipid oxidation, and nitrite and nitrate content were like healthy individuals. Our results suggest that long-term ERT in men with FD contributes to the reduction of a pro-inflammatory scenario and a decrease of oxidative damage in patients, reflecting greater control throughout the disease and in the multisystemic changes characteristic of this disorder. These findings lead us to believe that long-term ERT can improve the redox status and protect these individuals against oxidative and nitrative stress, as well as the inflammatory process.

Cutaneous manifestations of Fabry disease: A systematic review

Fabry disease (FD) is a rare X-linked lysosomal storage disorder resulting in potential debilitating accumulation of glycosphingolipids in organs such as skin, nerves, heart, kidneys, lungs, and the central nervous system. Skin is easily investigated and can guide clinicians to diagnose FD, minimizing delay of enzyme substitution therapy. This systematic review followed the PICO and PRISMA guidelines. Using Web of Science, PubMed, and Embase, a total of 968 studies were retrieved by January 1, 2024. All clinical studies describing the skin characteristics and abnormalities of FD patients were included. After inclusion of articles, the methodological quality was assessed using the QUADAS-2 critical appraisal checklist. Twenty-three studies were included. Different skin manifestations were described in FD patients. Fifteen studies described angiokeratomas, five studied telangiectasias, 13 studied sweat abnormalities (anhidrosis/hypohidrosis/hyperhidrosis), nine described lymphoedema, and two reported hair abnormalities. Sweat abnormalities were the most common skin manifestation, affecting 57.6% of patients with FD; angiokeratomas were observed in 51.5% of patients. A high prevalence (16.5%) of lymphoedema was seen in a large study (n = 5487). Skin involvement appeared age-dependent and increased with age. Quality assessment showed high or unclear risk of bias in 19/23 studies. We summarized data on skin manifestations in 10 757 FD patients. The pathogenesis of sweat abnormalities and the occurrence of cutaneous vascular lesions, such as angiokeratomas and telangiectasias, in only half of FD patients remains poorly understood. Enzyme replacement therapy generally did not reduce skin manifestations in FD patients. Direct comparisons between studies were challenging due to variations in reported outcomes.

Safety analysis of self-administered enzyme replacement therapy using data from the Fabry Outcome and Gaucher Outcome Surveys

BACKGROUND

Fabry disease and Gaucher disease are rare genetic disorders characterized by defective degradation of glycosphingolipids caused by enzymatic deficiencies in α-galactosidase A and β-glucocerebrosidase, respectively, and often require life-long treatment. Treatment options for these disorders include replacing the deficient enzymes via enzyme replacement therapy (ERT). Agalsidase alfa for Fabry disease and velaglucerase alfa for Gaucher disease are two ERT options with demonstrated efficacy, safety, and tolerability. ERT infusions administered by a health care provider (HCP) in the clinic/hospital, or at the patient's home are considered HCP-supported infusions. Self-administration of ERT (by patient, partner, relative, or caregiver) is optional in patients who tolerate the HCP-supported infusions at home and have a suitable home environment. This analysis explored the safety profiles of self-administered agalsidase alfa (202 patients) and velaglucerase alfa (30 patients) versus HCP-supported infusions using data from the Fabry Outcome Survey (FOS) and Gaucher Outcome Survey (GOS) registries.

RESULTS

The frequency of infusion-related reactions (IRRs) adverse events (AEs) recorded in the two registries was lower in patients self-administering (FOS: 4.5%, GOS: 0%) versus patients receiving HCP-supported infusions (FOS: 13.6%, GOS: 1.6%). In the FOS registry, AE rates per 100 patient-years (100PY) of follow-up were similar between the self-administration (7.99) and HCP-supported infusion (6.78) groups. In patients self-administering agalsidase alfa, cardiac disorders were the most frequently reported AEs (19 [9.4%] patients) and serious AEs (12 [5.9%]) and gastrointestinal disorders were the most frequently reported IRRs (3 [1.5%]). In the GOS registry, AE rates per 100PY were similar between self-administration (4.97) and HCP-supported infusion (4.67) groups. In patients self-administering velaglucerase alfa, skin and subcutaneous disorders (4 [13.3%]) and infections and infestations (2 [6.7%]) were the most reported AEs and serious AEs, respectively, and no IRRs were reported.

CONCLUSIONS

These findings suggest that self-administration of agalsidase alfa or velaglucerase alfa infusions are not associated with additional safety risks compared with HCP-supported infusions and are a suitable option for qualifying patients. Further research is warranted to support these findings and to explore further the long-term safety and efficacy of ERT self-administration. FOS trial registration: ClinicalTrials.gov, NCT03289065. Registered 01 April 2001, https://clinicaltrials.gov/study/NCT03289065 . GOS trial registration: ClinicalTrials.gov, NCT03291223. Registered 27 July 2010, https://classic.

CLINICALTRIALS

gov/ct2/show/NCT03291223 .

The Role of Kidney Biopsy in Fabry Disease

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the GLA gene, leading to α-galactosidase A deficiency and subsequent accumulation of glycosphingolipids, including globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3), in multiple organs. This accumulation can result in multisystemic disease and life-threatening complications. FD presents with a broad phenotypic spectrum, ranging from the classic form, with early and severe symptoms, to a later-onset form with variable manifestations. The severity of the disease in females is more variable due to X-chromosome inactivation (XCI). Renal involvement is a key feature, and kidney biopsy remains a valuable tool for diagnosing FD and assessing the extent of nephropathy. Although molecular genetic testing is the gold standard for diagnosis, kidney biopsy aids in confirming renal involvement, detecting coexisting conditions, and determining the pathogenicity of variants of uncertain significance (VUSs). Moreover, kidney biopsy can serve as a prognostic tool by identifying early markers of nephropathy, such as foot process effacement and glomerular sclerosis, which predict disease progression. Emerging technologies, including machine learning, offer the potential to enhance the analysis of renal histology, improving diagnostic accuracy and patient stratification. Despite the challenges posed by overlapping diseases and potential misdiagnoses, kidney biopsy remains an essential component of FD diagnosis and management, facilitating early detection, the monitoring of disease progression, and the evaluation of therapeutic responses.

Females with Fabry disease: an expert opinion on diagnosis, clinical management, current challenges and unmet needs

Females with Fabry disease (FD) often have a milder phenotype, later symptom onset, and slower disease progression than males, causing delayed diagnosis and undertreatment. A survey was conducted at nine Italian FD centers to evaluate routine management of females with FD; results were discussed at a meeting of eleven Italian specialists and recommendations developed. Of the 227 females managed by the physicians surveyed, 85% were diagnosed through family screening and 38.5% were symptomatic at presentation. Female patients usually underwent cardiac, renal, and neurologic monitoring, and measurement of plasma lyso-globotriaosylsphingosine (Gb3) levels at 6- or 12-month intervals. Treatment was initiated in 54%, mostly enzyme replacement therapy. Experts recommended screening all female relatives of index cases and evaluating all potentially affected organ systems. Diagnosis should be based on genetic analysis. Individualized monitoring of asymptomatic females must balance the need to detect organ damage while maintaining adherence. Treatment decisions should be based primarily on signs/symptoms of FD, but age, family screening results, GLA mutations, Gb3/lyso-Gb3 accumulation, and organ damage should be considered in asymptomatic females. More research on FD in females is needed and physicians should be aware of differences in the diagnosis, monitoring, and management of females vs. males with FD.

Fabry Disease and Its Different Phenotypes

Fabry disease (FD) is an X-linked genetic condition caused by variants in the GLA gene causing enzyme α-galactosidase A deficiency and accumulation of globotriaosylceramide (Gb3) in tissues such as the heart, kidneys, and the nervous system. This study reports a case series of patients with FD, highlighting the phenotypic diversity of the disease, which can be confused with other cardiological conditions. When properly indicated, genetic evaluation, combined with biomarker dosage and α-galactosidase enzymatic activity, is key for an accurate diagnosis. Early diagnosis of FD is fundamental for initiating treatments that can slow disease progression and prevent serious complications, reinforcing the need for greater awareness about this condition among cardiologists.

Treatment Beliefs Reflect Unmet Clinical Needs in Lysosomal Storage Diseases: An Opportunity for a Patient-Centered Approach

Despite life-long pharmacotherapy for many people affected by lysosomal storage diseases, no data are available on their beliefs about their treatments. Therapeutic options range from disease-specific, with varying levels of effectiveness, to purely supportive. This spectrum is illustrated by the three diseases Gaucher disease type 1 (effective disease-specific therapies), Fabry disease (disease-specific therapies with variable effectiveness), and mucopolysaccharidosis type III A/B (supportive care only). Employing the Necessity-Concerns Framework of the Beliefs in Medicine Questionnaire, we investigated intra- and intergroup variability in adults with Gaucher disease type 1, Fabry disease, and parents of children with mucopolysaccharidosis type III A/B. Participants rated necessity and concern items on a Likert scale, leading to categorization as accepting, skeptical, indifferent, or ambivalent. Self-reported demographic, disease-, and therapy-related data were also obtained. Eighty-one surveys were completed. Gaucher disease respondents (n = 15) were overwhelmingly categorized as accepting (high necessity, low concern). Female Fabry disease respondents (n = 43) were almost equally distributed over all categories except accepting. Male Fabry disease respondents (n = 16) were mostly ambivalent or accepting, indicating overall high necessity scores but varying concern. All mucopolysaccharidosis type III participants (n = 7) were categorized as indifferent (low necessity, low concern). The Beliefs in Medicine Questionnaire emerged as a valuable and feasibly employable tool for individual and group assessments in these populations. It reveals differences in beliefs aligned with current unmet medical needs. Expansion of this approach is warranted to optimize personalized counseling on therapeutic choices and to align drug development with the needs and beliefs of potential recipients.

Epidemiology and early predictors of Fabry nephropathy: evaluation of long-term outcomes from a national Fabry centre

BACKGROUND

Fabry disease is a rare genetic lysosomal storage disorder, whereby the accumulation of sphingolipids consequently leads to kidney structural damage and dysfunction. We explored the epidemiology of chronic kidney disease (CKD) among patients with Fabry disease at a major UK referral centre in Greater Manchester serving over 7 million people, to inform early predictors of kidney disease and possible treatment planning.

METHODS

Data were sourced from the electronic records of registered participants from November 2020 to February 2022 of adults diagnosed with Fabry disease, with at least 1 year of follow-up. Four hundred and five participants (female = 223, male = 182) met the initial eligibility criteria. Our study focused on identifying factors linked to incident CKD, with 395 evaluable individuals undergoing outcome analysis over a median of 6.4 years.

RESULTS

Findings concluded that 60.5% of participants received disease-modifying treatments, 29.7% experienced non-fatal cardiovascular events, 3.3% developed end-stage kidney disease (ESKD), and 7.3% died. Men had higher use of disease modifying therapy, progression to ESKD requiring kidney replacement therapy, cardiovascular events, and mortality compared to women. Subgroup analysis over 9 years revealed that older age, cardiovascular history, renin-angiotensin-aldosterone system inhibitor use, and higher urine albumin-to-creatinine ratio (uACR) were predictors of faster estimated glomerular filtration rate (eGFR) decline and increased mortality. At baseline, 47.8% of 249 patients with uACR data had CKD, and 25.4% of the remaining individuals developed CKD during follow-up, associated with higher uACR and lower, albeit normal eGFR levels.

CONCLUSION

Over 60% of Fabry disease patients are at lifetime risk of developing CKD, with a substantial risk of mortality, even with initially normal uACR and eGFR values.

MRI T2 Mapping of Dorsal Root Ganglia Reveals Increased T2 Relaxation Time in Classical Fabry Disease

Background/Objectives: Fabry disease (FD) is a rare X-linked lysosomal storage disorder characterised by progressive glycolipid accumulation affecting multiple organs, including the peripheral nervous system. The dorsal root ganglia (DRG) play a key role in Fabry-related neuropathy, but non-invasive biomarkers of DRG involvement and their association with overall disease severity remain limited. This study evaluated lumbosacral DRG T2 relaxation time (DRG-T2) in FD patients as a potential imaging biomarker of FD severity. Methods: In a prospective, single-centre study, 80 genetically confirmed FD patients underwent 3T MRI with quantitative T2 mapping of the lumbosacral DRG. DRG-T2 was analysed in relation to sex, genetic subtype and Fabry-specific biomarkers. Results: Results showed that DRG-T2 was higher in patients with classical FD mutations than in those with nonclassical mutations (p = 0.03). Furthermore, DRG-T2 showed a negative correlation with body weight (ρ = -0.31, p = 0.005) and BMI (ρ = -0.32, p = 0.004), while no associations were found with lyso-Gb3 levels or alpha-galactosidase A activity. The inter-rater and test-retest reliability of DRG-T2 were good to excellent (ICC = 0.76 and 0.89, respectively). Conclusions: These results demonstrate DRG-T2 as a marker of neuronal involvement, making it a strong and reliable imaging biomarker of disease severity in FD. However, future studies need to correlate its changes with clinical and histological studies.

Prevalence and Clinical Correlates of Cerebrovascular Alterations in Fabry Disease: A Cross-Sectional Study

Background/Objectives: Fabry disease (FD) is an inborn error of the glycosphingolipid metabolism with variable kidney, heart, and central nervous system (CNS) involvement. CNS-related FD manifestations include early ischemic stroke and white matter lesions (WMLs) related to cerebral small-vessel disease (CSVD), possibly resulting in cognitive impairment. We studied 40 adult FD patients (17 male) to assess: (i) prevalence of cerebrovascular and cognitive manifestations in FD and their correlation with heart and renal involvement; and (ii) the potential value of serum neurofilament light chain (NfL) levels as an indicator of WMLs in FD. Methods: Patients underwent detailed diagnostic assessment related to FD, also including Mainz Severity Score Index (MSSI), neuropsychological tests, brain MRI to assess WMLs by the modified Fazekas score (mFS), and NfL determination by single-molecule array (SiMoA) (n = 22 FD patients vs. 15 healthy controls). Results: Overall, 4 FD patients had a history of ischemic stroke and 13/32 patients (40.6%) had an mFS ≥ 1. Almost two-thirds of FD patients (27/39, 69.2%) showed impairment on at least one cognitive test. On univariate analysis, only a reduction in estimated glomerular filtration rate was associated with an increased likelihood of having WMLs on brain MRI. Serum NfL levels were higher in FD patients vs. controls, with a trend toward significance (p = 0.08). Conclusions: Mild-to-moderate CSVD is a characteristic brain "signature" in FD patients. Both cardiac and renal involvement correlate with WML load, but only renal involvement appears to be predictive of CNS damage. Brain microvascular damage is associated with mild cognitive impairment in FD, and serum NfL might represent a potential biomarker of CSVD in FD.

Fabry Disease and Inflammation: Potential Role of p65 iso5, an Isoform of the NF-κB Complex

Fabry disease (FD) is an X-linked lysosomal storage disease, caused by mutations in the GLA gene on the X chromosome, resulting in a deficiency of the lysosomal enzyme α-GAL. This leads to the progressive accumulation of Gb3 in cells, causing multi-systemic effects. FD has been classified as a subgroup of autoinflammatory diseases. NF-κB is a family of ubiquitous and inducible transcription factors that play critical roles in inflammation, in which the p65/p50 heterodimer is the most abundant. The glucocorticoid receptor (GR) represents the physiological antagonists in the inflammation process. A novel spliced variant of p65, named p65 iso5, which can bind the dexamethasone, enhancing GR activity, has been found. This study investigates the potential role of p65 iso5 in the inflammation of subjects with FD. We evaluated in peripheral blood mononuclear cells (PBMCs), from over 100 FD patients, the p65 iso5 mRNA level, and the protein expression. The results showed significantly lower p65 iso5 mRNA and protein expression levels compared to controls. These findings, along with the ability of p65 iso5 to bind dexamethasone and the regulation of the glucocorticoid response in the opposite way of p65, strongly suggest the involvement of p65 iso5 in the inflammatory response in FD.

In vivo confocal microscopic study of cornea verticillata and limbus deposits in patients with Fabry disease

Purpose

This study was aimed to investigate the microstructure characteristics of cornea verticillata and limbus deposits in patients with Fabry disease (FD) using in vivo confocal microscopy (IVCM).

Methods

A total of 60 eyes from 30 patients diagnosed with FD were examined and compared with 36 eyes from 18 healthy controls in this prospective, cross-sectional, controlled, single-center study. The initial assessment of cornea verticillata (CV) was conducted using slit-lamp microscopy. Subsequently, IVCM was performed to assess deposits in the corneal and limbal epithelium. We compared the differences between the sexes (heterozygous and hemizygous) and phenotypes (classical and non-classical).

Results

The epithelial deposit detection rate with IVCM was statistically higher (52/60, 86.67%) compared to the biomicroscopic evaluation of CV using a silt lamp (46/60, 76.67%) (p = 0.031). A higher prevalence of corneal epithelial deposits was observed in the classical phenotype as compared to the non-classical phenotype (p = 0.023). Surprisingly, cardiac variants previously lacking cornea verticillata show a high prevalence (85.71%) of corneal epithelial deposits under IVCM. The prevalence and severity of deposits, especially in limbal epithelial rete pegs, were higher in FD than in controls (p < 0.001).

Conclusion

Compared with slit-lamp microscopy, IVCM provides a more effective tool for examining the epithelial deposits in patients with FD. Patients with FD demonstrated a profound bilateral increase in corneal epithelial deposits and limbal hyperreflective cells compared to controls, with more prominent pathological changes observed in classical phenotype individuals. The high prevalence of epithelial deposits observed through IVCM in the cardiac variant highlights the essential ability of IVCM as an effective diagnostic tool.

Effects of Current Therapies on Disease Progression in Fabry Disease: A Narrative Review for Better Patient Management in Clinical Practice

Fabry disease (FD) is a rare lysosomal storage disorder that is characterized by renal, neurological, and cardiovascular dysfunction. Four treatments are currently available for patients with FD; three enzyme replacement therapies (ERTs; agalsidase alfa, agalsidase beta, and pegunigalsidase alfa) and one pharmacological chaperone (migalastat). This review focuses on the evidence for the benefits of ERTs and migalastat, and provides an overview of their impact on disease manifestations and quality of life (QoL). Agalsidase beta is associated with renal, neurological, and cardiovascular benefits, and may prevent renal disease progression. Agalsidase alfa provides stabilizing effects across all main organ systems, although minor sex-specific differences exist in patients with more advanced baseline disease. The benefits of agalsidase alfa and agalsidase beta are similar but depend on the extent of baseline disease. Some data indicate that agalsidase beta may be preferable over the longer term. Both agalsidase alfa and agalsidase beta are associated with improved gastrointestinal and pain symptoms, as well as improved QoL. Patients with advanced end-organ damage tend not to respond as optimally to ERTs as those who initiate ERTs before irreversible organ fibrosis develops, highlighting the need for early treatment initiation. Migalastat, which is only approved for patients with amenable missense gene variants, generally stabilizes renal parameters and provides cardiovascular benefits. Migalastat also improves diarrhea and pain, and stabilizes QoL (although ERT may be more effective for pain management), but the neurological effects of migalastat have not been studied. Real-world data raise concerns about effective in vivo amenability of some genetic variants. Future studies with direct treatment comparisons in patients with FD are needed.

A systematic literature review to evaluate the cardiac and cerebrovascular outcomes of patients with Fabry disease treated with agalsidase Beta

Background

Agalsidase beta is used to treat Fabry disease (FD); however, data on cardiac and cerebrovascular outcomes with agalsidase beta treatment come from studies with limited numbers of patients.

Methods

A systematic literature review of studies reporting on the efficacy and effectiveness of agalsidase beta in FD was conducted. Studies were identified in searches of MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials from January 2000-June 2022. Outcomes of interest included cardiac structure and mass, cardiac events, and cerebrovascular events.

Results

Fifty-two citations (41 studies) were included. Reductions in interventricular septal thickness (IVST) and/or left ventricular posterior wall thickness (LVPWT) were demonstrated in six studies (follow-up 1-6 years, n = 4 using echocardiography, n = 2 cardiac MRI). IVST ranged from 12.1-14.9 mm at baseline and 10.8-14.1 mm at follow-up (all p < 0.05). LVPWT ranged from 11.7-16.0 mm at baseline and 10.7-13.0 mm at follow-up (all p < 0.05). Significant reductions in cardiac mass were demonstrated after 1 year of treatment in a single-arm study using cardiac MRI [left ventricular mass (LVM) 193-178 g; LVM index 102-94 g/m2; both p < 0.05]. Rates of composite cardiac events (3.8%-24.0%; four studies, follow-up 2-10 years) and cerebrovascular events (0.0%-18.9%; 12 studies, follow-up 1-10 years) were numerically lower than rates for placebo (follow-up 3 years).

Conclusion

Literature over the last 20 years indicates that agalsidase beta treatment may lead to stabilization or regression of cardiac structural thickness and mass, and reduction in cardiac and cerebrovascular events relative to placebo.

Urinary Myeloid Bodies as a Biomarker for Early Diagnosis and Monitoring of Enzyme Replacement Therapy in Fabry Disease

Introduction

The prevalence of urinary myeloid bodies in Fabry disease patients and their correlation with renal involvement remains unclear.

Methods

This single-center, retrospective study included 25 patients with Fabry disease and 27 controls. We analyzed 24-h urine samples for the presence of urinary myeloid bodies and evaluated clinical data, including serum creatinine, estimated glomerular filtration rate (eGFR), 24-h urinary protein levels, α-Gal A, and Lyso-GL-3. Seven Fabry patients underwent analysis of urine samples before and after 1 year of enzyme replacement therapy (ERT).

Results

Urinary myeloid bodies were detected in 84% of Fabry patients (21 out of 25), with no significant gender differences. None of the healthy controls or patients with other renal disease patients had urinary myeloid bodies. Among the Fabry patients with myeloid bodies, 48% had no proteinuria, and 52% were in CKD1 stage G1. Furthermore, urinary myeloid bodies were detected in 4 patients under the age of 20, despite the absence of or only minimal proteinuria, and these patients all exhibited a substantial number of myeloid bodies. After 1 year of ERT, significant reductions in both the count (p = 0.043) and area ratio (p = 0.028) of myeloid bodies were observed.

Conclusion

Urinary myeloid bodies are specific to Fabry disease and are associated with early renal injury, even in the absence of proteinuria. These findings suggest that urinary myeloid bodies may serve as a noninvasive biomarker for the early diagnosis of Fabry disease and for monitoring the efficacy of ERT.

Renal and multisystem effectiveness of 3.9 years of migalastat in a global real-world cohort: Results from the followME Fabry Pathfinders registry

Fabry disease is a progressive, X-linked lysosomal disorder caused by reduced or absent α-galactosidase A activity due to GLA variants. The effects of migalastat were examined in a cohort of 125 Fabry patients with migalastat-amenable GLA variants in the followME Pathfinders registry (EUPAS20599), an ongoing, prospective, patient-focused registry evaluating outcomes for current Fabry disease treatments. We report annualised estimated glomerular filtration rate (eGFR) and Fabry-associated clinical events (FACEs) in a cohort of patients who had received ≥3 years of migalastat treatment in a real-world setting. As of August 2022, 125 patients (60% male) had a mean migalastat exposure of 3.9 years. At enrolment, median age was 58 years (males, 57; females, 60) with a mean eGFR of 83.7 mL/min/1.73 m2 (n = 122; males, 83.7; females, 83.8) and a median left ventricular mass index of 115.1 g/m2 (n = 61; males, 131.2; females, 98.0). Mean (95% confidence interval) eGFR annualised rate of change in the overall cohort (n = 116) was -0.9 (-10.8, 9.9) mL/min/1.73 m2/year with a similar rate of change observed across patients with varying levels of kidney function at enrolment. Despite population age and baseline morbidity, 80% of patients did not experience a FACE during the mean 3.9 years of migalastat exposure. The incidence of renal, cardiac, and cerebrovascular events was 2.0, 83.2, and 4.1 events per 1000 patient-years, respectively. These data support a role of migalastat in preserving renal function and multisystem effectiveness during ≥3 years of migalastat treatment in this real-world Fabry population.

A real-world pharmacovigilance analysis for agalsidase beta: findings from the FDA adverse event reporting database

BACKGROUND

Fabry disease (FD), an X-linked lysosomal disorder, is marked by a lack of alpha-galactosidase A (α-Gal A). Agalsidase beta, a recombinant form of α-Gal A, is fundamental to enzyme replacement therapy for FD but requires close monitoring for adverse events (AEs).

RESEARCH DESIGN AND METHODS

This study retrospectively analyzed the Food and Drug Administration Adverse Event Reporting System (FAERS) database for agalsidase beta-related AEs. Disproportionality analysis was used for data analysis.

RESULTS

A total of 7,611 AE reports for agalsidase beta were analyzed. The most common AEs included pyrexia, pain, chills, malaise, and nausea. Several system organ classes including Cardiac Disorders, General Disorders and Administration Site Conditions, and Vascular Disorders, showed positive signals. Subgroup analysis by gender revealed differences in AE reporting, with males exhibiting a higher reporting odds ratio for certain preferred terms such as Renal Transplant and Drug Specific Antibody Present.

CONCLUSION

The FAERS database analysis of agalsidase beta AEs identified a significant number of cardiovascular, renal, and cerebrovascular system-related reports. While agalsidase beta is generally well-tolerated, the study underscores the necessity for gender-specific treatment approaches due to the higher incidence of certain AEs in males.

Advancing Genetic Testing in Kidney Diseases: Report From a National Kidney Foundation Working Group

About 37 million people in the United States have chronic kidney disease, a disease that encompasses multiple causes. About 10% or more of kidney diseases in adults and as many as 70% of selected chronic kidney diseases in children are expected to be explained by genetic causes. Despite the advances in genetic testing and an increasing understanding of the genetic bases of certain kidney diseases, genetic testing in nephrology lags behind other medical fields. More understanding of the benefits and logistics of genetic testing is needed to advance the implementation of genetic testing in chronic kidney diseases. Accordingly, the National Kidney Foundation convened a Working Group of experts with diverse expertise in genetics, nephrology, and allied fields to develop recommendations for genetic testing for monogenic disorders and to identify genetic risk factors for oligogenic and polygenic causes of kidney diseases. Algorithms for clinical decision making on genetic testing and a road map for advancing genetic testing in kidney diseases were generated. An important aspect of this initiative was the use of a modified Delphi process to reach group consensus on the recommendations. The recommendations and resources described herein provide support to nephrologists and allied health professionals to advance the use of genetic testing for diagnosis and screening of kidney diseases.

Impact of the Covid19 pandemic on health-related quality of life in patients with Fabry disease - implications for future care of patients with rare diseases

Background

The worldwide Covid19 pandemic caused by the rapid spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) represented a unique challenge for patients and healthcare professionals. Patients with chronic rare diseases had to face novel burdens, like the inability to perform regular on-site visits or even difficulties in the supply of medication. Patients with Fabry disease (FD) are affected by a variety of organ manifestations leading to physical but also psychological burden and limitations, which are usually presented in low health-related quality of life (HR-QoL). We sought to examine the impact of the Covid19 pandemic on HR-QoL in patients with FD and their implications for the future care of patients with rare diseases.

Methods

This single-center study included patients seen shortly prior to and after the peak of the Covid19 pandemic in 2020 at our study site. All patients had a confirmed genetic diagnosis of FD. Subjects with presumed apathogenic to benigne genetic variants in the GLA gene were excluded. The Short Form (36) Health Survey (SF-36) was used to obtain patients'self-reported outcome. Clinical data and SF-36 scores were collected and analysed for the time period prior to and after the peak of the pandemic.

Results

In total, 60 patients (mean age 47.9 ± 15 years, 53.3 % male) were included. The majority presented with a pathogenic gene variant (63.3 %) associated with classic phenotype. At baseline, 66.7 % were on enzyme replacement therapy (ERT), and 21.7 % on chaperone therapy. Predominant organ manifestations were cardiac (42/60, 70.0 %) and neurological (39/60, 65.0 %). After paired comparison prior and post peak of the pandemic in 2020, all eight items of the SF-36 score showed a numeric decline. Three items presented with a intergroup difference: social functioning (72.5 ± 29.3 vs. 64.8 ± 29.3, p = 0.012), energy/fatigue (56.8 ± 21.7 vs. 48.3 ± 23.9, p < 0.001), and role limitations due to physical health (64.2 ± 42.0 vs. 51.1 ± 45.5, p = 0.007).Subgroup analysis (regarding gender, age, and treatment) revealed that especially male and older (≥50 years) patients with FD showed reductions in multiple categories of HR-QoL. The item "energy/fatigue" presented significant declines among all subgroups.

Conclusions

The worldwide Covid19 pandemic had a persistent negative affect on self-reported HR-QoL in patients with FD, including both mental and physical aspects. It remains unclear to what extend the disease itself and accompanying circumstances including local and governmental actions and restrictions contributed to these deteriorations. Our findings stress the importance for meticulous and constant interdisciplinary care including psychosocial aspects in patients with chronic progressive diseases as well as the need for a change in mindset concerning future medical care including further progress in digitalisation and a strengthening of the remote health care sector by authorities.

Long-read sequencing enables comprehensive molecular genetic diagnosis of Fabry disease

BACKGROUND

The clinical diagnosis of Fabry Disease (FD) can be challenging due to the clinical heterogeneity, especially in females. Patients with FD often experience a prolonged interval between the onset of symptoms and receiving a diagnosis. Genetic testing is the gold standard for precise diagnosis of FD, however conventional genetic testing could miss deep intronic variants and large deletions or duplications. Although next-generation sequencing, which analyzes numerous genes, has been successfully used for FD diagnosis and can detect complex variants, an effective and rapid tool for identifying a wide range of variants is imminent, contributing to decrease the diagnostic delay.

METHODS

The comprehensive Analysis of FD (CAFD) assay was developed for FD genetic diagnosis, employing long-range PCR coupled with long-read sequencing to target the full-length GLA gene and its flanking regions. Its clinical performance was assessed through a comparative analysis with Sanger sequencing.

RESULTS

Genetic testing was performed on 82 individuals, including 48 probands and 34 relatives. The CAFD assay additionally identified variants in two probands: one had a novel and de novo pathogenic variant with a 1715 bp insertion in intron 4, and the other carried two deep intronic VUS variants in cis-configuration also in intron 4. In total, CAFD identified 47 different variants among 48 probands. Of these, 42 (89.36%, 42/47) were pathogenic, while 5 (10.64%, 5/47) were VUS. Sixteen (34.04%, 16/47) of the variants were novel, including 15 SNV/Indels and one large intronic insertion. Pedigree analysis of 21 probands identified four de novo disease-causing variants. Hence, FD exhibits not only variable clinical presentations but also a wide spectrum of variants. Utilizing a comprehensive testing algorithm for diagnosing FD, which includes enzyme activity, clinical features, and genetic testing, the diagnostic yield of CAFD is 97.92% (47/48), which is higher than that of conventional Sanger sequencing, at 95.83% (46/48).

CONCLUSION

The duration between initial clinical presentation and diagnosis remains long and winding. CAFD provides precise diagnosis for a wide spectrum of GLA variants, promoting timely diagnosis and appropriate treatment for FD patients.

Anderson-Fabry Disease: Focus on Ophthalmological Implications

Fabry disease (FD) is a rare X-linked lysosomal storage disorder with a broad spectrum of clinical manifestations, including severe complications, such as end-stage renal disease, hypertrophic cardiomyopathy, and cerebrovascular disease. Enzyme replacement therapy (ERT), when initiated early, has been shown to reduce the incidence of severe events and slow disease progression. In the classic form, characterized by the absence of α-galactosidase A (α-Gal A) enzyme activity, diagnosis is straightforward. However, when residual activity is present, the delayed and less obvious presentation can make diagnosis more challenging. Ophthalmological alterations, which can be detected through non-invasive examinations may play a crucial role in correctly assessing the patient in terms of diagnosis and prognosis, particularly in these atypical cases. Recognizing these ocular signs allows for timely intervention with ERT, leading to improved patient outcomes. This review highlights the importance of ophthalmological findings in FD, emphasizing their role in diagnosis and treatment planning. By raising awareness among ophthalmologists and healthcare specialists, this review aims to improve disease management, offering tools for early detection and better long-term prognosis in patients with FD.

Different diseases, different needs: Patient preferences for gene therapy in lysosomal storage disorders, a probabilistic threshold technique survey

BACKGROUND

Gene therapy is currently in development for several monogenetic diseases including lysosomal storage disorders. Limited evidence is available on patient preferences for gene therapy in this population. In this study, we compare gene therapy-related risk tolerance between people affected by three lysosomal storage diseases currently faced with different therapeutic options and prognoses.

METHODS

A survey including the probabilistic threshold technique was developed in which respondents were asked to choose between gene therapy and the current standard of care. The attributes included to establish participants' risk tolerance were previously identified in focus groups of affected people or their representatives, namely: risk of mild side effects, severe side effects, the need for additional medication, and the likelihood of long-term effectiveness. The survey was distributed among people receiving outpatient care for type 1 Gaucher disease (good prognosis with current treatment options), Fabry disease (varying prognosis with current treatment options, XY-genotype on average more severely affected than XX), and parents representing people with severe forms of mucopolysaccharidosis type III A/B (poor prognosis, no disease-specific therapy available).

RESULTS

A total of 85 surveys were completed (15 Gaucher disease respondents, 62 Fabry disease respondents (17 self-identifying male), eight parents of ten people with mucopolysaccharidosis type III). Disease groups with higher disease severity trended towards higher risk tolerance: Gaucher disease respondents were most cautious and predominantly preferred the current standard of care as opposed to MPS III representatives who were more risk tolerant. Respondents with Fabry disease were most heterogeneous in their risk tolerance, with male participants being more risk tolerant than female participants. Long-term effectiveness was the attribute in which respondents tolerated the least risk.

CONCLUSIONS

People affected by a lysosomal storage disease associated with a poorer prognosis and less effective current treatment options trended towards more risk tolerance when choosing between gene therapy and the current standard of care. This study shows the importance of involvement of patient preferences before and during the development process of new treatment modalities such as gene therapy for rare diseases, to ensure that innovative therapies align with the wishes and needs of people affected by these diseases.

Fabry disease: a rare disorder calling for personalized medicine

Fabry Disease (FD) is a genetic disease caused by a deficiency in the activity of lysosomal galactosidase A (α-GalA), an enzyme responsible for the catabolism of globotriaosylceramide (Gb3). Since lysosomes are present throughout the body and play a crucial role in catabolism and recycling of cytosolic compounds, FD can affect multiple organs and result in various symptoms, including renal, cardiovascular, neurological, cutaneous, and ophthalmic manifestations. Due to the nonspecific symptoms and the rarity of FD, it is often diagnosed late in life. However, introducing targeted therapies such as enzyme replacement therapy (ERT) and chaperone therapy has significantly improved FD's natural history and prognosis by restoring α-GalA enzyme activity. Despite the advancements, there are limitations to the currently available therapies, which has prompted research into new potential treatments for FD, including alternative forms of enzyme replacement therapy, substrate reduction therapy, mRNA therapy, and genetic therapy. In this review, we analyze the epidemiology, pathophysiology, and treatment of FD, with particular emphasis on promising therapeutic opportunities that could shift the treatment of this rare disease from a standardized to a personalized approach soon.

Fabry Disease with Genetic Variants of Unknown Significance and Concomitant Immunoglobulin A Nephropathy

INTRODUCTION

The diagnosis of Fabry disease (FD) with genetic variants of unknown significance (VUSs) is relatively difficult. We explored patients with novel VUS variants and concomitant immunoglobulin A nephropathy (IgAN) to improve the understanding of VUS.

METHODS

The study retrospectively investigated patients with genetically confirmed FD. Probands with VUS were selected from the database of FD patients who underwent genetic analysis. Demographic, clinicopathological, and laboratory data from probands and family members were collected and analyzed.

RESULTS

Fourteen probands and their family members were included in the study. The probands were divided into group 1 (patients with VUS, n = 5) and group 2 (patients with pathologic/likely pathologic variants, n = 9). The group 1 included 2 missense mutations and 1 deletion mutation, while the group 2 included 6 missense mutations and 2 deletion mutations. There were no significant differences in gender, age, serum creatinine, eGFR, and proteinuria between the two groups. IgA deposition with myeloid bodies was found in all VUS patients. The cardiac involvement in group 2 was more severe than that in group 1. Seven families performed the pedigree analysis, and after the comprehensive evaluation, two GLA variants (c.479C>A, p.Ala160Asp; c.1032-1058 del, p.Ser345_Met353del) were upgraded from VUS to the likely pathogenic.

CONCLUSION

The clinical manifestations of FD are heterogeneous. FD often coexists with nephrotic disorders, such as IgAN and MCD. Comprehensive evaluation, especially tissue-specific biopsy, is necessary for patients with GLA-VUSs. Two GLA variants (c.479C>A, p.Ala160Asp; c.1032-1058 del, p.Ser345_Met353del) were upgraded from VUS to the likely pathogenic after the comprehensive evaluation.

No differences in native T1 of the renal cortex between Fabry disease patients and healthy subjects in cardiac-dedicated native T1 maps

BACKGROUND

Fabry disease (FD) is an X-linked inherited lysosomal storage disease that is caused by deficient activity of the enzyme alpha-galactosidase A. Cardiovascular magnetic resonance (CMR) imaging can detect cardiac sphingolipid accumulation using native T1 mapping. The kidneys are often visible in cardiac CMR native T1 maps; however, it is currently unknown if the maps can be used to detect sphingolipid accumulation in the kidneys of FD patients. Therefore, the aim of this study was to evaluate if cardiac-dedicated native T1 maps can be used to detect sphingolipid accumulation in the kidneys.

METHODS

FD patients (n = 18, 41 ± 10 years, 44% (8/18) male) and healthy subjects (n = 38, 41 ± 16 years, 47% (18/38) male) were retrospectively enrolled. Native T1 maps were acquired at 1.5T using modified Look-Locker inversion recovery research sequences. Native T1 values were measured by manually delineating regions of interest (ROI) in the renal cortex, renal medulla, heart, spleen, blood, and liver. Endo- and epicardial borders were delineated in the myocardium and averaged across all slices. Blood ROIs were placed in the left ventricular blood pool in the midventricular slice.

RESULTS

There were no differences in native T1 between the FD patients and the healthy subjects in the renal cortex (1034 ± 88 ms vs 1056 ± 59 ms, p = 0.29), blood (1614 ± 111 ms vs 1576 ± 100 ms, p = 0.22), spleen (1143 ± 45 ms vs 1132 ± 70 ms, p = 0.54), or liver (568 ± 49 ms vs 557 ± 47 ms, p = 0.41). Native myocardial T1 was lower in FD patients compared to healthy subjects (951 ± 79 vs 1006 ± 38, p<0.01), and higher in the renal medulla (1635 ± 144 vs 1514 ± 81, p<0.01).

CONCLUSION

Compared to healthy subjects, patients with FD and cardiac involvement showed no differences in native T1 of the renal cortex. FD patients had higher native T1 in the renal medulla, which is not totally explained by differences in blood native T1 but may reflect a hyperfiltration state in the development of renal failure. The findings suggest that sphingolipid accumulation in the renal cortex in FD patients could not be detected with cardiac-dedicated research native T1 maps.

In Silico Modeling of Fabry Disease Pathophysiology for the Identification of Early Cellular Damage Biomarker Candidates

Fabry disease (FD) is an X-linked lysosomal disease whose ultimate consequences are the accumulation of sphingolipids and subsequent inflammatory events, mainly at the endothelial level. The outcomes include different nervous system manifestations as well as multiple organ damage. Despite the availability of known biomarkers, early detection of FD remains a medical need. This study aimed to develop an in silico model based on machine learning to identify candidate vascular and nervous system proteins for early FD damage detection at the cellular level. A combined systems biology and machine learning approach was carried out considering molecular characteristics of FD to create a computational model of vascular and nervous system disease. A data science strategy was applied to identify risk classifiers by using 10 K-fold cross-validation. Further biological and clinical criteria were used to prioritize the most promising candidates, resulting in the identification of 36 biomarker candidates with classifier abilities, which are easily measurable in body fluids. Among them, we propose four candidates, CAMK2A, ILK, LMNA, and KHSRP, which have high classification capabilities according to our models (cross-validated accuracy ≥ 90%) and are related to the vascular and nervous systems. These biomarkers show promise as high-risk cellular and tissue damage indicators that are potentially applicable in clinical settings, although in vivo validation is still needed.

Experts' Opinion in Fabry Disease Management and the Unmet Medical Need: The Saudi Perspective

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by α-galactosidase A gene mutations. Its global incidence ranges from 1:40,000 to 1:170,000. This expert review evaluates the available guidelines, the status of diagnosed but untreated patients with FD, and the challenges in diagnosing and managing FD in the Kingdom of Saudi Arabia (KSA). An advisory board meeting (ABM) was conducted in two phases, with a survey that aimed to receive insights on the current unmet needs in the management of patients with FD in November 2022, and a second, offline meeting in February 2023. The goal of this ABM was to discuss current unmet needs in the management of Fabry patients in the Kingdom of Saudi Arabia. In the first ABM, experts opined on the best practices in the diagnosis, screening, and management of FD for healthcare professionals. These opinions on the management of FD relied on data from research and expert clinical judgments. In the second ABM, the same panel discussed different aspects of FD diagnosis, treatment, and management in the member countries of the Gulf Cooperation Council. The experts discussed the stigma associated with FD, patient awareness and knowledge, genetic screening, biomarkers, and home infusion therapy. They reviewed international guidelines and clinical criteria for enzyme replacement therapy (ERT). Furthermore, they also discussed the diagnosis of FD in men and women, the current guidelines followed for monitoring patients with FD, monitoring untreated patients with FD, Fabry Stabilization IndeX (FASTEX) as an assessment tool for the diagnosis of FD, FD management in KSA, challenges encountered while prescribing ERT in patients with FD, and the clinical criteria for starting ERT. The discussions led to the conclusion that currently, ERT is the only available therapy to manage FD and research should be focused on the early diagnosis and management of FD.

Establishing Treatment Effectiveness in Fabry Disease: Observation-Based Recommendations for Improvement

Fabry disease (FD, OMIM #301500) is caused by pathogenic GLA gene (OMIM #300644) variants, resulting in a deficiency of the α-galactosidase A enzyme with accumulation of its substrate globotriaosylceramide and its derivatives. The phenotype of FD is highly variable, with distinctive disease features and course in classical male patients but more diverse and often nonspecific features in non-classical and female patients. FD-specific therapies have been available for approximately two decades, yet establishing robust evidence for long-term effectiveness remains challenging. This review aims to identify the factors contributing to this lack of robust evidence for the treatment of FD with enzyme replacement therapy (ERT) (agalsidase-alfa and -beta and pegunigalsidase alfa) and chaperone therapy (migalastat). Major factors that have been identified are study population heterogeneity (concerning sex, age, phenotype, disease stage) and differences in study design (control groups, outcomes assessed), as well as the short duration of studies. To address these challenges, we advocate for patient matching to improve control group compatibility in future FD therapy studies. We recommend international collaboration and harmonization, facilitated by an independent FD registry. We propose a stepwise approach for evaluating the effectiveness of novel treatments, including recommendations for surrogate outcomes and required study duration.

Clinical outcomes in patients switching from agalsidase beta to migalastat: A Fabry Registry analysis

Fabry Registry data were analyzed among 83 agalsidase beta-treated patients with Fabry disease who switched to migalastat. Outcomes (estimated glomerular filtration rate [eGFR], urine protein-creatinine ratio [UPCR], plasma globotriaosylceramide [GL-3], plasma globotriaosylsphingosine [lyso-GL-3], interventricular septal wall thickness [IVST], left posterior wall thickness [LPWT], left ventricular mass index [LVMI]) were assessed using linear mixed models to estimate annual change over time in the pre- and postswitch periods. eGFR decreased throughout both periods (preswitch: -0.85 mL/min/1.73 m2/year; postswitch: -1.96 mL/min/1.73 m2/year; both p < 0.0001), with steeper decline postswitch (ppre/post = 0.01) in both classic and late-onset patients. UPCR increased significantly postswitch (ppre/post = 0.003) among classic patients and was stable in both periods among late-onset patients. GL-3 trajectories worsened postswitch across phenotypes (ppre/post = 0.0005 classic, 0.02 late-onset). LPWT was stable preswitch (0.07 mm/year, p = 0.25) and decreased postswitch (-0.51 mm/year, p = 0.0005; ppre/post = 0.0009), primarily among late-onset patients. IVST and LVMI slopes varied significantly by phenotype. Among classic patients, IVST and LVMI were stable and decreasing, respectively preswitch and increasing postswitch (ppre/post = 0.02 IVST, 0.01 LVMI). Among late-onset patients, IVST significantly decreased postswitch (ppre/post = 0.0003); LVMI was stable over time (ppre/post = 0.89). Ultimately, eGFR and GL-3 trajectories worsened postswitch across phenotypes, while UPCR and cardiac measures worsened among classic and stabilized/improved among late-onset patients. These findings indicate variability in long-term outcomes after switching from ERT to migalastat, underscoring the importance of careful monitoring.

Clinical outcomes in elderly patients receiving agalsidase alfa treatment in the Fabry Outcome Survey

BACKGROUND AND OBJECTIVES

Treatment with agalsidase alfa in patients with Fabry disease is most effective when initiated early in the disease course; however, the clinical benefits in elderly patients are less well established. This analysis assesses outcomes in patients aged 65 years or older from the Fabry Outcome Survey (FOS) who were treated with agalsidase alfa.

METHODS

FOS data were extracted for adult patients aged 65 years or older who received agalsidase alfa, had baseline data and at least 3 years of post-baseline data, and had undergone no renal transplantation and/or dialysis before treatment. The data of patients who had undergone renal transplantation and/or dialysis during follow-up were excluded from estimated glomerular filtration rate (eGFR) analysis after the date of the renal transplantation and/or dialysis. Adult patients were stratified into two groups: those who started treatment before 65 years of age and who were still being treated when aged 65 years or older (group A), and those who started treatment when aged 65 years or older (group B). Mean annual changes in left ventricular mass index (LVMI), eGFR and proteinuria were assessed in group A (before and after the age of 65 years to understand if there was an age-related effect once patients turned 65 years of age) and in group B.

RESULTS

Estimated mean (standard error [SE]) annual changes in LVMI were 0.46 (0.26) g/m2.7 and 0.21 (0.42) g/m2.7 in patients in group A when they were younger than 65 years and when they were aged 65 years or older, respectively, and 0.12 (0.65) g/m2.7 in patients in group B. For eGFR, mean (SE) annual changes were 0.83 (2.12) mL/min/1.73 m2 and 2.64 (2.18) mL/min/1.73 m2 in patients in group A when they were younger than 65 years and when they were aged 65 years or older, respectively, and 2.31 (1.44) mL/min/1.73 m2 in patients in group B. Proteinuria remained relatively stable in both subgroups of group A (before and after the age of 65 years) and group B.

CONCLUSIONS

Continuation and initiation of agalsidase alfa treatment in patients aged 65 years or older with Fabry disease were associated with stabilization of proteinuria and minimal increases in cardiac (LVMI) and renal (eGFR) outcomes.

Inflammatory cytokine expression in Fabry disease: impact of disease phenotype and alterations under enzyme replacement therapy

Objectives

The aim of this study is to explore the expression of inflammatory cytokines (ICs) in Fabry disease (FD), the correlation between ICs and FD phenotypes, and the impact of enzyme replacement therapy (ERT) on IC expression.

Methods

We recruited 67 FD patients and 44 healthy controls (HCs) and detected concentrations of the following ICs: interferon-γ, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12P70, IL-17A, IL-17F, IL-22, tumor necrosis factor (TNF)-α, and TNF-β. We also analyzed the impact of ERT on IC expression in FD patients and the relationship between IC expression and sex, genotype, phenotype, disease burden, and biomarkers.

Results

Most ICs were significantly higher in FD patients than in HCs. A number of ICs were positively correlated with clinical aspects, including disease burden (Mainz Severity Score Index [MSSI]) and cardiac and renal markers. IL-8 was higher in the high MSSI (P-adj=0.026*) than in the low MSSI.

Conclusions

ICs were upregulated in FD patients, indicating the role of the innate immune process in FD etiology. ERT ameliorated FD-related inflammatory activation, at least to some extent. IC expression was positively correlated with disease burden and clinical markers in FD. Our findings indicated that the inflammatory pathway may be a promising therapeutic target for FD.

Reduction in kidney function decline and risk of severe clinical events in agalsidase beta-treated Fabry disease patients: a matched analysis from the Fabry Registry

Background

Patients with Fabry disease (FD, α-galactosidase A deficiency or absence) accumulate glycosphingolipids, leading to progressive dysfunction of kidneys, heart and nervous system. Generalizable real-world outcomes following agalsidase beta treatment initiation outside trials are limited. We investigated the associations of long-term agalsidase beta treatment with estimated glomerular filtration rate (eGFR) changes over time and the risk of developing a composite clinical event in a matched analysis of treated and untreated patients with FD.

Methods

Agalsidase beta-treated adult patients (aged ≥16 years) from the Fabry Registry and adult untreated patients from a natural history cohort were matched 1:1 and X:X (with one occurrence and multiple occurrences of each untreated patient, respectively) by sex, phenotype, age and (for eGFR slope analysis) baseline eGFR. Outcomes included eGFR slope over 5 years and composite clinical event risk (cardiovascular, cerebrovascular or renal event, or death) over 10+ years. As a surrogate indicator of therapeutic response in paediatric patients, the percentage experiencing normalization in plasma globotriaosylceramide (GL-3) from treatment initiation was assessed in patients aged 2 to <16 years.

Results

Overall, eGFR slopes for 1:1-matched untreated and treated adult patients [122 pairs (72.1% male)] were -3.19 and -1.47 mL/min/1.73 m2/year, respectively (reduction in rate of decline = 53.9%, P = .007), and for X:X-matched [122 untreated/950 treated (59.4% male)] were -3.29 and -1.56 mL/min/1.73 m2/year, respectively (reduction in rate of decline = 52.6%, P < .001). Agalsidase beta treatment was associated with lower risk of clinical events, with hazard ratios of 0.41 (P = .003) and 0.67 (P = .008) for 1:1-matched and X:X-matched analyses, respectively. Plasma GL-3 declined markedly in paediatric patients and normalized in most within 6 months of treatment initiation.

Conclusion

Agalsidase beta treatment preserves kidney function and delays progression to severe clinical events among adult patients with FD. Plasma GL-3 levels analysed in paediatric patients showed normalization of elevated pre-treatment levels in most patients.

Genome-wide expression analysis in a Fabry disease human podocyte cell line

Fabry disease (FD) is an X-linked lysosomal disease caused by an enzyme deficiency of alpha-galactosidase A (α-gal A). This deficiency leads to the accumulation of glycosphingolipids in lysosomes, resulting in a range of clinical symptoms. The complex pathogenesis of FD involves lysosomal dysfunction, altered autophagy, and mitochondrial abnormalities. Omics sciences, particularly transcriptomic analysis, comprehensively understand molecular mechanisms underlying diseases. This study focuses on genome-wide expression analysis in an FD human podocyte model to gain insights into the underlying mechanisms of podocyte dysfunction. Human control and GLA-edited podocytes were used. Gene expression data was generated using RNA-seq analysis, and differentially expressed genes were identified using DESeq2. Principal component analysis and Spearman correlation have explored gene expression trends. Functional enrichment and Reporter metabolite analyses were conducted to identify significantly affected metabolites and metabolic pathways. Differential expression analysis revealed 247 genes with altered expression levels in GLA-edited podocytes compared to control podocytes. Among these genes, 136 were underexpressed, and 111 were overexpressed in GLA-edited cells. Functional analysis of differentially expressed genes showed their involvement in various pathways related to oxidative stress, inflammation, fatty acid metabolism, collagen and extracellular matrix homeostasis, kidney injury, apoptosis, autophagy, and cellular stress response. The study provides insights into molecular mechanisms underlying Fabry podocyte dysfunction. Integrating transcriptomics data with genome-scale metabolic modeling further unveiled metabolic alterations in GLA-edited podocytes. This comprehensive approach contributes to a better understanding of Fabry disease and may lead to identifying new biomarkers and therapeutic targets for this rare lysosomal disorder.

How Do Physical Activity and Exercise Affect Fabry Disease? Exploring a New Opportunity

BACKGROUND

Fabry disease (FD) is a multisystem, monogenic, X-linked storage disorder caused by mutations in the GLA gene, resulting in reduced alfa-galactosidase A enzyme activity. This effect leads to the accumulation of glycosphingolipids, particularly globotriaosylceramide, in various tissues, including the heart, kidney, vasculature, smooth muscle, and peripheral nervous system. Hemizygous males are usually more severely affected than females, in whom random inactivation of an X chromosome may lead to variable phenotype.

SUMMARY

Among the manifestations of FD, exercise intolerance is commonly diagnosed but often underestimated, even though it significantly limits quality of life, especially in young patients. This review primarily discusses the various pathophysiological mechanisms involved in exercise intolerance in FD patients, such as altered muscle composition, compromised cardiopulmonary framework, and peripheral neuropathy. Secondarily, it explores the potential effect of available therapy, including enzyme replacement therapy and chaperone therapy (migalastat), in reducing exercise intolerance while considering the potential impact of physical activity and exercise training as adjunctive treatments.

CONCLUSION

Exercise intolerance has a major impact on the well-being of people with FD. Exercise training can play an important role in addition to drug therapy.

Fabry disease Enzyme Enhancement on migalastat Study: FEES

BACKGROUND

There is limited information on the α-galactosidase A (α-Gal-A) in vivo response in Fabry patients receiving migalastat. In this single centre study, we evaluated changes from baseline in α-Gal A activity, lyso-Gb3 and other assessments in patients on migalastat.

RESULTS

79 patients were recruited (48 M:31F; median duration receiving migalastat 3.8 years [range = 0.4-14.9 years]). N215S was the commonest genotype in males (67 %) and females (29 %). Leukocyte α-Gal-A showed a positive change from baseline in males (n = 4; median = 20.05); females (n = 8; median = 26). Of these, 3 males and 1 female had N215S (median = 16.7), while 7 females and 1 male had other genotypes (median = 26). No significant changes observed in plasma α-Gal-A. Cross-sectional analysis of post-baseline data confirmed leukocyte α-Gal-A enhancement in males (n = 47; median = 20); females (n = 30; median = 72); N215S (n = 41; median = 29) and other genotypes (n = 36; median = 36.5). Plasma and dried blood spot (DBS) lyso-Gb3 correlated at baseline and post-baseline (r = 0.77 and r = 0.96; p=<0.0001).

CONCLUSIONS

In the 12 patients with paired data, there was a median enzyme enhancement of 17.4 (relative change = 2.54) and 33 (relative change = 0.87) in males and in females, respectively. The cross-sectional post-baseline data in 47 patients corroborated leukocyte α-Gal-A enhancement on migalastat. Plasma and DBS lyso-Gb3 correlated well supporting DBS utility for disease monitoring.

Unveiling the untreated: development of a database algorithm to identify potential Fabry disease patients in Germany

BACKGROUND

Fabry disease (FD), an X-linked lysosomal storage disorder, is caused by mutations in the gene encoding α-galactosidase A, resulting in lysosomal accumulation of globotriaosylceramide and other glycosphingolipids. Early detection of FD is challenging, accounting for delayed diagnosis and treatment initiation. This study aimed to develop an algorithm using a logistic regression model to facilitate early identification of patients based on ICD-10-GM coding using a German Sickness Fund Database.

METHODS

The logistic regression model was fitted on a binary outcome variable based on either a treated FD cohort or a control cohort (without FD). Comorbidities specific to the involved organs were used as covariates to identify potential FD patients with ICD-10-GM E75.2 diagnosis but without any FD-specific medication. Specificity and sensitivity of the model were optimized to determine a likely threshold. The cut-point with the largest values for the Youden index and concordance probability method and the lowest value for closest to (0,1) was identified as 0.08 for each respective value. The sensitivity and specificity for this cut-point were 80.4% and 79.8%, respectively. Additionally, a sensitivity analysis of the potential FD patients with at least two codes of E75.2 diagnoses was performed.

RESULTS

A total of 284 patients were identified in the potential FD cohort using the logistic regression model. Most potential FD patients were < 30 years old and female. The identification and incidence rates of FD in the potential FD cohort were markedly higher than those of the treated FD cohort.

CONCLUSIONS

This model serves as a tool to identify potential FD patients using German insurance claims data.

Characterization of the plasma proteomic profile of Fabry disease: Potential sex- and clinical phenotype-specific biomarkers

Fabry disease (FD) is a X-linked rare lysosomal storage disorder caused by deficient α-galactosidase A (α-GalA) activity. Early diagnosis and the prediction of disease course are complicated by the clinical heterogeneity of FD, as well as by the frequently inconclusive biochemical and genetic test results that do not correlate with clinical course. We sought to identify potential biomarkers of FD to better understand the underlying pathophysiology and clinical phenotypes. We compared the plasma proteomes of 50 FD patients and 50 matched healthy controls using DDA and SWATH-MS. The >30 proteins that were differentially expressed between the 2 groups included proteins implicated in processes such as inflammation, heme and haemoglobin metabolism, oxidative stress, coagulation, complement cascade, glucose and lipid metabolism, and glycocalyx formation. Stratification by sex revealed that certain proteins were differentially expressed in a sex-dependent manner. Apolipoprotein A-IV was upregulated in FD patients with complications, especially those with chronic kidney disease, and apolipoprotein C-III and fetuin-A were identified as possible markers of FD with left ventricular hypertrophy. All these proteins had a greater capacity to identify the presence of complications in FD patients than lyso-GB3, with apolipoprotein A-IV standing out as being more sensitive and effective in differentiating the presence and absence of chronic kidney disease in FD patients than renal markers such as creatinine, glomerular filtration rate and microalbuminuria. Identification of these potential biomarkers can help further our understanding of the pathophysiological processes that underlie the heterogeneous clinical manifestations associated with FD.

Genetic variants of unknown significance in alpha-galactosidase A: Cellular delineation from Fabry disease

Fabry disease (FD) is an X-linked multiorgan disorder caused by variants in the alpha-galactosidase A gene (GLA). Depending on the variant, disease phenotypes range from benign to life-threatening. More than 1000 GLA variants are known, but a link between genotype and phenotype in FD has not yet been established for all. p.A143T, p.D313Y, and p.S126G are frequent examples of variants of unknown significance (VUS). We have investigated the potential pathogenicity of these VUS combining clinical data with data obtained in human cellular in vitro systems. We have analyzed four different male subject-derived cell types for alpha-galactosidase A enzyme (GLA) activity and intracellular Gb3 load. Additionally, Gb3 load in skin tissue as well as clinical data were studied for correlates of disease manifestations. A reduction of GLA activity was observed in cells carrying p.A143T compared with controls (p < 0.05). In cells carrying the p.D313Y variant, a reduced GLA activity was found only in endothelial cells (p < 0.01) compared with controls. No pathological changes were observed in cells carrying the p.S126G variant. None of the VUS investigated caused intracellular Gb3 accumulation in any cell type. Our data of aberrant GLA activity in cells of p.A143T hemizygotes and overall normal cellular phenotypes in cells of p.D313Y and p.S126G hemizygotes contribute a basic science perspective to the clinically highly relevant discussion on VUS in GLA.

Arrhythmogenesis in Fabry Disease

PURPOSE OF REVIEW

Fabry Disease (FD) is a rare lysosomal storage disorder characterised by multiorgan accumulation of glycosphingolipid due to deficiency in the enzyme α-galactosidase A. Cardiac sphingolipid accumulation triggers various types of arrhythmias, predominantly ventricular arrhythmia, bradyarrhythmia, and atrial fibrillation. Arrhythmia is likely the primary contributor to FD mortality with sudden cardiac death, the most frequent cardiac mode of death. Traditionally FD was seen as a storage cardiomyopathy triggering left ventricular hypertrophy, diastolic dysfunction, and ultimately, systolic dysfunction in advanced disease. The purpose of this review is to outline the current evidence exploring novel mechanisms underlying the arrhythmia substrate.

RECENT FINDINGS

There is growing evidence that FD cardiomyopathy is a primary arrhythmic disease with each stage of cardiomyopathy (accumulation, hypertrophy, inflammation, and fibrosis) contributing to the arrhythmia substrate via various intracellular, extracellular, and environmental mechanisms. It is therefore important to understand how these mechanisms contribute to an individual's risk of arrhythmia in FD. In this review, we outline the epidemiology of arrhythmia, pathophysiology of arrhythmogenesis, risk stratification, and cardiac therapy in FD. We explore how advances in conventional cardiac investigations performed in FD patients including 12-lead electrocardiography, transthoracic echocardiography, and cardiac magnetic resonance imaging have enabled early detection of pro-arrhythmic substrate. This has allowed for appropriate risk stratification of FD patients. This paves the way for future work exploring the development of therapeutic initiatives and risk prediction models to reduce the burden of arrhythmia.

Cerebral arteriopathies of childhood and stroke - A focus on systemic arteriopathies and pediatric fibromuscular dysplasia (FMD)

Systemic vascular involvement in children with cerebral arteriopathies is increasingly recognized and often highly morbid. Fibromuscular dysplasia (FMD) represents a cerebral arteriopathy with systemic involvement, commonly affecting the renal and carotid arteries. In adults, FMD diagnosis and classification typically relies on angiographic features, like the 'string-of-beads' appearance, following exclusion of other diseases. Pediatric FMD (pFMD) is considered equivalent to adult FMD although robust evidence for similarities is lacking. We conducted a comprehensive literature review on pFMD and revealed inherent differences between pediatric and adult-onset FMD across various domains including epidemiology, natural history, histopathophysiology, clinical, and radiological features. Although focal arterial lesions are often described in children with FMD, the radiological appearance of 'string-of-beads' is highly nonspecific in children. Furthermore, children predominantly exhibit intimal-type fibroplasia, common in other childhood monogenic arteriopathies. Our findings lend support to the notion that pFMD broadly reflects an undefined heterogenous group of monogenic systemic medium-or-large vessel steno-occlusive arteriopathies rather than a single entity. Recognizing the challenges in categorizing complex morphologies of cerebral arteriopathy using current classifications, we propose a novel term for describing children with cerebral and systemic vascular involvement: 'cerebral and systemic arteriopathy of childhood' (CSA-c). This term aims to streamline patient categorization and, when coupled with advanced vascular imaging and high-throughput genomics, will enhance our comprehension of etiology, and accelerate mechanism-targeted therapeutic developments. Lastly, in light of the high morbidity in children with cerebral and systemic arteriopathies, we suggest that investigating for systemic vascular involvement is important in children with cerebral arteriopathies.