Use of a rare disease registry for establishing phenotypic classification of previously unassigned GLA variants: a consensus classification system by a multispecialty Fabry disease genotype-phenotype workgroup

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.

Experience with cascade screening: A comprehensive family pedigree analysis of two index patients with Fabry disease

The wide range of clinical symptoms observed in patients with Fabry disease (FD) often leads to delays in diagnosis and initiation of treatment. Delayed initiation of therapy may result in end-organ damage, such as chronic renal failure, hypertrophic cardiomyopathy, and stroke. Although some tools are available to identify undiagnosed patients, new comprehensive screening methods are needed. In this study, the outcomes of the cascade screening applied to three index cases with FD from 2 familes were investigated. In the pedigree analysis, 280 individuals were included; out of them, 131 individuals underwent genetic testing and cascade screening for FD. During the screening program, a total of 45 individuals were diagnosed, with a diagnostic ratio of 1:15. The average age at diagnosis for all individuals was 30.9 ± 17.7 years, and %25 were pediatric cases (mean age 9.5 ± 5.9 years). Thirty affected relatives were diagnosed from the two index cases in Family 1 and 15 individuals were diagnosed from one index case in Family 2. There were 13 consanguineous marriages observed among 2 pedigres, in two both spouses  were affected, leading to two homozygous affected daughters in one couple. In regions where there is a high prevalence of consanguineous marriages, implementing the cascade screening approach to identify all individuals at risk can be beneficial for patients with FD, specifically women and children.

Pegunigalsidase alfa: a novel, pegylated recombinant alpha-galactosidase enzyme for the treatment of Fabry disease

Fabry disease, a rare X-linked genetic disorder, results from pathogenic variants in GLA, leading to deficient lysosomal α-galactosidase A enzyme activity and multi-organ manifestations. Since 2001, enzyme replacement therapy (ERT), using agalsidase alfa or agalsidase beta, has been the mainstay treatment, albeit with limitations such as rapid clearance and immunogenicity. Pegunigalsidase alfa, a novel PEGylated recombinant alpha-galactosidase, offers promise as an alternative. Produced in plant cells, pegunigalsidase alfa exhibits enhanced stability, prolonged half-life, and reduced immunogenicity due to pegylation. A phase 1/2 clinical trial demonstrated Gb3 clearance from renal capillary endothelial cells and its 48-month extension study revealed notable outcomes in renal function preservation. Three phase 3 clinical trials (BRIDGE, BRIGHT, and BALANCE) have shown favorable efficacy and safety profile, although caution is warranted in interpreting the results of BRIDGE and BRIGHT which lacked control groups. In BALANCE, the pivotal phase 3 trial comparing pegunigalsidase alfa with agalsidase beta, an intention-to-treat analysis of the eGFR decline over 2 years showed that the intergroup difference [95%confidence interval] in the median slope was -0.36 mL/min/1.73 m2/year [-2.44; 1.73]. The confidence interval had a lower limit above the prespecified value of -3 mL/min/1.73 m2/year and included zero. Despite challenges such as occasional hypersensitivity reactions and immune-complex-mediated glomerulonephritis, pegunigalsidase alfa approval by the European Medicines Agency and the Food and Drug Administration represents a significant addition to Fabry disease therapeutic landscape providing an option for patients in whom enzyme replacement therapy with current formulations is poorly tolerated or poorly effective.

Fabry Disease: Cardiac Implications and Molecular Mechanisms

PURPOSE OF REVIEW

This review explores the interplay among metabolic dysfunction, oxidative stress, inflammation, and fibrosis in Fabry disease, focusing on their potential implications for cardiac involvement. We aim to discuss the biochemical processes that operate in parallel to sphingolipid accumulation and contribute to disease pathogenesis, emphasizing the importance of a comprehensive understanding of these processes.

RECENT FINDINGS

Beyond sphingolipid accumulation, emerging studies have revealed that mitochondrial dysfunction, oxidative stress, and chronic inflammation could be significant contributors to Fabry disease and cardiac involvement. These factors promote cardiac remodeling and fibrosis and may predispose Fabry patients to conduction disturbances, ventricular arrhythmias, and heart failure. While current treatments, such as enzyme replacement therapy and pharmacological chaperones, address disease progression and symptoms, their effectiveness is limited. Our review uncovers the potential relationships among metabolic disturbances, oxidative stress, inflammation, and fibrosis in Fabry disease-related cardiac complications. Current findings suggest that beyond sphingolipid accumulation, other mechanisms may significantly contribute to disease pathogenesis. This prompts the exploration of innovative therapeutic strategies and underscores the importance of a holistic approach to understanding and managing Fabry disease.

Frequency of Fabry disease in chronic kidney disease patients including patients on renal replacement therapy in Korea

BACKGROUND

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by the deficient activity of α-galactosidase (α-Gal A), affecting multiple organs including kidney. In this study, we aimed to determine the prevalence of FD in patients with chronic kidney disease (CKD) including those on renal replacement therapy in Korea.

METHODS

This is a national, multicenter, observational study performed between August 24, 2017 and February 28, 2020. Patients with the presence of proteinuria or treated on dialysis were screened by measuring the α-Gal A enzyme activity using either dried blood spot or whole blood, and plasma globotriaosylsphingosine (lyso-GL3) concentration. A GLA gene analysis was performed in patients with low α-Gal A enzyme activity or increased plasma lyso-GL3 concentration.

RESULTS

Of 897 screened patients, 405 (45.2%) were male and 279 (31.1%) were on dialysis. The α-Gal A enzyme activity was measured in 891 patients (99.3%), and plasma lyso-GL3 concentration was measured in all patients. Ten patients were eligible for a GLA gene analysis: eight with low α-Gal A enzyme activity and two with increased plasma lyso-GL3 concentration. The GLA mutations were analyzed in nine patients and one patient was found with a pathogenic mutation. Therefore, one patient was identified with FD, giving a prevalence of 0.1% (1 of 897) in this CKD population.

CONCLUSION

Although the prevalence of FD in the CKD population was low (0.1%), screening tests are crucial to detect potential diseases in patients with relatives who can benefit from early treatment.

Glycogen Storage Disease: Expert Opinion on Clinical Diagnosis Revisited after Molecular Testing

This study sought to analyze whether an accurate diagnosis of the type and subtype of hepatic Glycogen Storage Diseases (GSDs) could be performed based on general clinical and biochemical aspects via comparing the proposed diagnostic hypotheses with the molecular results. Twelve physicians with experience in hepatic GSDs reviewed 45 real cases comprising a standardized summary of clinical and laboratory data. There was no relation between the hit rate and the time since graduation, the time of experience in GSD, and the number of patients treated during their careers. The average assertiveness was 47%, with GSD Ia and Ib being the best-identified types, while no expert correctly identified GSD IXc. Underage investigation for later manifestations, incomplete clinical description, and complementary analysis, the overvaluation of a specific clinical finding ("false positive") or the discarding of the diagnosis in the absence of it ("false negative"), as well as the lack of knowledge of the rarest GSD types, may have impacted the accuracy of the assessment. This study emphasized that characteristics considered as determinants in identifying the specific types or subtypes of GSD are not exclusive, thus becoming factors that may have induced the evaluators to misdiagnose.

Brain MRI correlations with disease burden and biomarkers in Fabry disease

OBJECTIVE

To quantitatively evaluate cerebral small vessel disease (CSVD) in brain magnetic resonance imaging (MRI) and its correlation with disease burden and markers in Fabry disease, a rare X-linked lysosomal storage disease.

METHODS

We collected brain MRI data from seventy-one Chinese patients with Fabry disease. CSVD was evaluated using an age-related white matter change rating scale, Fazekas scale, enlarged perivascular spaces grading scale, lacunar infarction scale, Microbleed Anatomical Rating Scale, global cortical atrophy scale, and small-vessel disease score. Factors associated with MRI lesions, including sex, clinical subtype, disease severity, disease burden, genotype, and biomarkers, were also analyzed.

RESULTS

Of 71 patients, 16 (22.5%) experienced ischemic stroke. The incidences of lacunar infarctions, white matter hyperintensities, and cerebral microbleeds were 55%, 62%, and 33%, respectively. The abnormal MRI group had later disease onset, longer disease duration, and a higher Mainz Severity Score Index (p < 0.05) than the normal MRI group. Patients with more severe clinical phenotypes also had higher CVSD-related scores. Sex and GLA mutational type were not closely associated with brain MRI lesions. Of the disease markers, the Mainz Severity Score Index and plasma globotriaosylsphingosine (Lyso-Gb3) were closely correlated with the majority of the MRI scores, whereas α-galactosidase A activity was not.

CONCLUSION

Brain MRI revealed progressive lacunar infarctions, white matter hyperintensities, and decreased brain volume in patients with Fabry disease. Brain MRI lesions were closely related to onset-age; disease duration, severity, burden; and plasma Lyso-Gb3. However, they were not associated with sex, α-galactosidase A activity, or GLA mutation type.

Sex Differences in Anderson-Fabry Cardiomyopathy: Clinical, Genetic, and Imaging Analysis in Women

Anderson-Fabry Disease (AFD) is a rare, systemic lysosomal storage disease triggered by mutations in the GLA gene, leading to α-galactosidase A (α-Gal A) deficiency. The disease's X-linked inheritance leads to more severe, early-onset presentations in males, while females exhibit variable, often insidious, manifestations, notably impacting cardiac health. This study aims to examine gender-based AFD cardiac manifestations in correlation with the variant type: classical (CL), late-onset (LO), or variants of uncertain significance (VUS). We analyzed data from 72 AFD patients (53 females, 19 males) referred to the "G. Rodolico" University Hospital, employing enzyme activity measurements, genetic analysis, periodic lyso-Gb3 monitoring, comprehensive medical histories, and advanced cardiac imaging techniques. Statistical analysis was performed using SPSS version 26. Our AFD cohort, with an average age of 45 ± 16.1 years, comprised 12 individuals with hypertrophy (AFD-LVH) and 60 without (AFD-N). Women, representing about 75% of the subjects, were generally older than men (47.2 ± 16.2 vs. 38.8 ± 14.6, p = 0.046). In the female group, 17% had CL variants, 43.3% LO, and 39.6% had VUS, compared to 21.1%, 36.8%, and 31.6% in the male group, respectively. Females exhibited significantly higher α-Gal A values (median 7.9 vs. 1.8 nmol/mL/h, p < 0.001) and lower lyso-Gb3 levels (1.5 [IQR 1.1-1.7] vs. 1.9 [1.5-17.3] nmol/L, p = 0.02). Regarding the NYHA class distribution, 70% of women were in class I and 28% in class II, compared to 84% and 16% of men, respectively. Among women, 7.5% exhibited ventricular arrhythmias (10.5% in men), and 9.4% had atrial fibrillation (10.5% in men). Cardiac MRIs revealed fibrosis in 57% of examined women, compared to 87% of men. Even among patients without LVH, significant differences persisted in α-Gal A and lyso-Gb3 levels (p = 0.003 and 0.04), as well as LVMi (61.5 vs. 77.5 g/sqm, p = 0.008) and GLS values (-20% vs. -17%, p = 0.01). The analysis underscored older age, decreased lyso-Gb3 deposition, reduced hypertrophy, and lesser GLS compromise in females, suggesting later disease onset. Severe cardiac patterns were associated with classic variants, while more nuanced manifestations were noted in those with VUS. Early GLS impairment in males, irrespective of hypertrophy, emphasized the role of subclinical damage in AFD.

A Cross-Sectional Study of the Dermatological Manifestations of Patients with Fabry Disease and the Assessment of Angiokeratomas with Multimodal Imaging

Fabry disease (FD) is a multisystemic X-linked lysosomal storage disease that presents with angiokeratomas (AKs). Our objective was to investigate the clinical and morphologic features of AKs and to present two experimental techniques, multispectral imaging (MSI) and non-linear microscopy (NLM). A thorough dermatological examination was carried out in our 26 FD patients and dermoscopic images (n = 136) were evaluated for specific structures. MSI was used for the evaluation of AKs in seven patients. NLM was carried out to obtain histology samples of two AKs and two hemangiomas. Although AKs were the most common manifestation, the majority of patients presented an atypical distribution and appearance, which could cause a diagnostic challenge. Dermoscopy revealed lacunae (65%) and dotted vessels (56%) as the most common structures, with a whitish veil present in only 25%. Autofluorescence (405 nm) and diffuse reflectance (526 nm) images showed the underlying vasculature more prominently compared to dermoscopy. Using NLM, AKs and hemangiomas could be distinguished based on morphologic features. The clinical heterogeneity of FD can result in a diagnostic delay. Although AKs are often the first sign of FD, their presentation is diverse. A thorough dermatological examination and the evaluation of other cutaneous signs are essential for the early diagnosis of FD.

Population Frequency of Undiagnosed Fabry Disease in the General Population

Introduction

Fabry disease is an X-linked disorder that results from pathogenic GLA variants and can now be treated. Most studies of its population frequency have examined only males or attendees at kidney failure or cardiac clinics. This study determined the prevalence of undiagnosed Fabry disease from predicted pathogenic GLA variants in the general population.

Methods

The Genome Aggregation Database (gnomAD) was examined for predicted pathogenic GLA variants based on variant rarity (≤5), and transcript effect in 4 computational tools (CADD >20, PP2 >0.95, SIFT <0.05, Mutation Taster - Disease-causing) and amino acid conservation in vertebrates in a Clustal.

Results

Predicted pathogenic variants in GLA occurred in 1 in 3225 of the gnomAD population and 1 in 3478 of its control subset. Predicted pathogenic variants were more common in women than expected (3.1:1), which is consistent with men being excluded from gnomAD because of Fabry complications. Predicted pathogenic variants were not found in members of this cohort with South Asian, Ashkenazim, or Finnish ancestries. Variants identified as pathogenic in the Fabry database were found in 1 in 2651 individuals of the gnomAD database and pathogenic variants from ClinVar in 1 in 4420.

Discussion

The population frequency of 1 in 3225 for undiagnosed men and women with Fabry disease still represents an underestimate because our pathogenicity criteria were rigorous, the cohort did not include already-diagnosed individuals, and whole exome sequencing does not detect intronic variants and large deletions. This study confirms that Fabry disease is more common than previously recognized and still underdiagnosed especially in women.

Global reach of over 20 years of experience in the patient-centered Fabry Registry: Advancement of Fabry disease expertise and dissemination of real-world evidence to the Fabry community

Fabry disease (FD, α-galactosidase A deficiency) is a rare, progressive, complex lysosomal storage disorder affecting multiple organ systems with a diverse spectrum of clinical phenotypes, particularly among female patients. Knowledge of its clinical course was still limited in 2001 when FD-specific therapies first became available and the Fabry Registry (NCT00196742; sponsor: Sanofi) was initiated as a global observational study. The Fabry Registry has now been operational for over 20 years, overseen by expert Boards of Advisors, and has collected real-world demographic and longitudinal clinical data from more than 8000 individuals with FD. Leveraging the accumulating evidence base, multidisciplinary collaborations have resulted in the creation of 32 peer-reviewed scientific publications, which have contributed to the greatly expanded knowledge on the onset and progression of FD, its clinical management, the role of sex and genetics, the outcomes of enzyme replacement therapy with agalsidase beta, and prognostic factors. We review how the Fabry Registry has evolved from its inception to become the largest global source of real-world FD patient data, and how the generated scientific evidence has helped to better inform the medical community, individuals living with FD, patient organizations, and other stakeholders. The patient-centered Fabry Registry fosters collaborative research partnerships with the overarching goal of optimizing the clinical management of patients with FD and is well positioned to add to its past achievements.

Anderson-Fabry disease cardiomyopathy: an update on epidemiology, diagnostic approach, management and monitoring strategies

Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder caused by deficient activity of the enzyme alpha-galactosidase. While AFD is recognized as a progressive multi-system disorder, infiltrative cardiomyopathy causing a number of cardiovascular manifestations is recognized as an important complication of this disease. AFD affects both men and women, although the clinical presentation typically varies by sex, with men presenting at a younger age with more neurologic and renal phenotype and women developing a later onset variant with more cardiovascular manifestations. AFD is an important cause of increased myocardial wall thickness, and advances in imaging, in particular cardiac magnetic resonance imaging and T1 mapping techniques, have improved the ability to identify this disease non-invasively. Diagnosis is confirmed by the presence of low alpha-galactosidase activity and identification of a mutation in the GLA gene. Enzyme replacement therapy remains the mainstay of disease modifying therapy, with two formulations currently approved. In addition, newer treatments such as oral chaperone therapy are now available for select patients, with a number of other investigational therapies in development. The availability of these therapies has significantly improved outcomes for AFD patients. Improved survival and the availability of multiple agents has presented new clinical dilemmas regarding disease monitoring and surveillance using clinical, imaging and laboratory biomarkers, in addition to improved approaches to managing cardiovascular risk factors and AFD complications. This review will provide an update on clinical recognition and diagnostic approaches including differentiation from other causes of increased ventricular wall thickness, in addition to modern strategies for management and follow-up.

Supporting the Diagnosis of Fabry Disease Using a Natural Language Processing-Based Approach

In clinical practice, the consideration of non-specific symptoms of rare diseases in order to make a correct and timely diagnosis is often challenging. To support physicians, we developed a decision-support scoring system on the basis of retrospective research. Based on the literature and expert knowledge, we identified clinical features typical for Fabry disease (FD). Natural language processing (NLP) was used to evaluate patients' electronic health records (EHRs) to obtain detailed information about FD-specific patient characteristics. The NLP-determined elements, laboratory test results, and ICD-10 codes were transformed and grouped into pre-defined FD-specific clinical features that were scored in the context of their significance in the FD signs. The sum of clinical feature scores constituted the FD risk score. Then, medical records of patients with the highest FD risk score were reviewed by physicians who decided whether to refer a patient for additional tests or not. One patient who obtained a high-FD risk score was referred for DBS assay and confirmed to have FD. The presented NLP-based, decision-support scoring system achieved AUC of 0.998, which demonstrates that the applied approach enables for accurate identification of FD-suspected patients, with a high discrimination power.

The Spanish Fabry women study: a retrospective observational study describing the phenotype of females with GLA variants

BACKGROUND

Fabry disease (FD) is an X-linked condition caused by variants in the GLA gene. Since females have two X chromosomes, they were historically thought to be carriers. Although increased knowledge has shown that females often develop the disease, data from Spain and other countries reported that females were undertreated. The aim of this study was to provide a wider and more recent description of the disease characteristics and associated management of females with a GLA variant in a Spanish cohort.

RESULTS

Ninety-seven females from 12 hospitals were included in this retrospective study. Mean age was 50.1 ± 17.2 years. Median follow-up time from GLA variant identification was 36.1 months, and most (70.1%) were identified through family screening. Variants associated with classic/non-classic phenotypes were similarly distributed (40.2%/53.6%). Missense variants were the most prevalent (n = 84, 86.6%). In the overall group, 70.4% had major organ involvement (i.e., cardiac, renal, cerebrovascular, peripheral nervous system or gastrointestinal), and 47.3% also had typical Fabry signs (angiokeratoma, cornea verticillata or increased plasma lyso-Gb3). Cardiac involvement was the most prevalent (49.5%) and the main reason for treatment initiation. A total of 33 (34%) patients received disease-specific therapy, 55% of whom were diagnosed by family screening. Females carrying variants associated with a classic phenotype had higher frequencies of clinical manifestations (92.3%) and were predominant in the treated subgroup (69.7%). Despite this, there were 34 untreated females (56.7% of total untreated), with both phenotypes represented, who had major organ involvement, with 27 of cardiac, renal or cerebrovascular nature. Age or comorbidities in this subgroup were comparable to the treated subgroup (P = 0.8 and P = 0.8, respectively).

CONCLUSIONS

Efforts have been made in recent years to diagnose and treat timely Fabry females in Spain. A high percentage of females with pathogenic variants, regardless of their associated phenotype, will likely develop disease. A proportion of females with severe disease in this cohort received specific treatment. Still a significant number of females, even with same profile as the treated ones, who may be eligible for treatment according to European recommendations, remained untreated. Reasons for this merit further investigation.

Distinctive accumulation of globotriaosylceramide and globotriaosylsphingosine in a mouse model of classic Fabry disease

Fabry disease (FD) is an inherited disease caused by deficient α-galactosidase A activity that is characterized by the accumulation of globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3). Although plasma lyso-Gb3 is a sensitive biomarker of FD, the correlation between its concentration and clinical symptoms remains unclear. To clarify the influence of plasma Gb3 and lyso-Gb3 in a symptomatic Gla ^tm Tg(CAG-A4GALT) FD mouse model, the total contents of Gb3, lyso-Gb3 and their analogs in various organs and plasma were determined in mice with early- (5-week-old) and late-stage (20-week-old) renal dysfunction. A marked increase in total Gb3 content in the heart, kidneys, spleen, liver, small intestine, lungs, brain, and plasma was observed in the 20-week-old mice compared to that in 5-week-old mice. In contrast, the increase in lyso-Gb3 was relatively small, and the total content in the lungs and plasma was unchanged. Lyso-Gb3 analogs {lyso-Gb3(-2) and lyso-Gb3(+18)} and Gb3 analogs {Gb3(-2) and Gb3(+18)} were observed in all organs and plasma at both ages, and the percentages of the analogs were unique to specific organs. The pattern of 37 Gb3 analogs/isoforms of liver Gb3 corresponded well with that of plasma Gb3. Although the analog pattern of plasma lyso-Gb3 did not resemble that of any organ lyso-Gb3, the relative content {lyso-Gb3: lyso-Gb3(-2)} in the sum of all organs corresponded well to that of the plasma at both ages. These data indicate that liver Gb3 may contribute to the plasma Gb3 level, while plasma lyso-Gb3 may be released from all organs, and the capacity of the plasma lyso-Gb3 pool may reach a maximum at an early stage of renal dysfunction.

Late-onset Fabry disease due to a new (p.Pro380Leu) pathogenic variant of GLA Gene

Fabry disease is a rare X-linked lysosomal storage disorder due to pathogenic variants of the galactosidase alpha (GLA) gene, leading to a deficiency of alpha-galactosidase A. The inadequate enzymatic activity leads to progressive glycosphingolipids accumulation within tissues and subsequent multi-systemic dysfunction, with predominant involvement of heart, kidney, and nervous system. Two subtypes are recognized: the classic type and the late-onset type. We here describe the clinical characteristics of a patient with late-onset Fabry disease carrying a not previously identified GLA gene variant. This 50-year-old man came to hospital because of an acute ischemic stroke. He also complained of acroparesthesia and had angiokeratomas in the nape and the back. Blood alpha-galactosidase A activity was low, plasmatic lyso-Gb3 level was borderline, cardiac MRI showed cardiac fibrosis, brain MRI documented cerebrovascular disease, and skin biopsy revealed small fiber neuropathy without globotriaosylceramide-3 skin deposits. Genetic study by means of targeted next-generation sequencing analysis disclosed a missense substitution c.1139C>T (p.Pro380Leu) in the GLA gene. We suggest that this novel variant should be considered as pathogenic and associated with a late-onset variant of Fabry disease with a predominant neurological phenotype.

Balance control impairments in Fabry disease

Background

Fabry disease (FD) is a rare inherited lysosomal storage disorder caused by the deficiency of the enzyme alpha-galactosidase A. This deficiency leads to an accumulation of glycosphingolipids leading to progressive and multisystemic disease, including renal, cardiac, and neurological damages. FD may also have neuro-otological and visual impairments, which can generate postural control alterations, inner ear, and vision being involved in this function. This study aimed to evaluate the impact of FD on postural control.

Methods

In total, fourteen adult patients (8 men/6 women, mean age = 37.6 ± 11.4 years) and two children (mean age = 11 years) with FD and 19 healthy adults (12 men/7 women, mean age = 36.5 ± 16.9 years) and two healthy children (mean age = 10.5 years) took part in this study. Postural control was evaluated by a sensory organization test combining three visual situations (eyes open, eyes closed, and sway referenced visual surround motion) with two platform situations (stable platform and sway referenced platform motion), aiming to calculate a composite equilibrium score (CES), a high score being representative of good postural control. Somatosensory (R^SOM), visual (R^VIS), and vestibular (R^VEST) contributions to postural control were calculated, a low score reflecting a poor use of the indicated sensory input.

Results

The CES was lower in adult patients with FD compared with the healthy subjects (p < 0.001). R^VIS (p = 0.001) and R^VEST (p = 0.003) were lower in patients with FD compared with the control group, whereas no difference in R^SOM was observed.

Conclusion

Inner ear and visual pathologies associated with the central nervous system impairments are factors of postural control impairments. Physical activities, which can also be rehabilitative, by maintaining or increasing the weight of proprioception, may help diminish dependency on altered sensorial inputs.

An expert consensus on practical clinical recommendations and guidance for patients with classic Fabry disease

Fabry disease is an X-linked inherited lysosomal disorder that causes accumulation of glycosphingolipids in body fluids and tissues, leading to progressive organ damage and reduced life expectancy. It can affect both males and females and can be classified into classic or later-onset phenotypes. In classic Fabry disease, α-galactosidase A (α-Gal A) activity is absent or severely reduced and disease manifestations have an early onset that can affect multiple organs. In contrast, in later-onset Fabry disease, patients have residual α-Gal A activity and clinical features are primarily confined to the heart. Individualized therapeutic goals in Fabry disease are required due to varying phenotypes and patient characteristics, and the wide spectrum of disease severity. An international group of expert physicians convened to discuss and develop practical clinical recommendations for disease- and organ-specific therapeutic goals in Fabry disease, based on expert consensus and evidence identified through a structured literature review. Biomarkers reflecting involvement of various organs in adult patients with classic Fabry disease are discussed and consensus recommendations for disease- and organ-specific therapeutic goals are provided. These consensus recommendations should support the establishment of individualized approaches to the management of patients with classic Fabry disease by considering identification, diagnosis, and initiation of disease-specific therapies before significant organ involvement, as well as routine monitoring, to reduce morbidity, optimize patient care, and improve patient health-related quality of life.

Renoprotective Effect of Agalsidase Alfa: A Long-Term Follow-Up of Patients with Fabry Disease

Fabry disease is a rare lysosomal storage disorder caused by mutations in the GLA gene, which, without treatment, can cause significant renal dysfunction. We evaluated the effects of enzyme replacement therapy with agalsidase alfa on renal decline in patients with Fabry disease using data from the Fabry Outcome Survey (FOS) registry. Male patients with Fabry disease aged >16 years at agalsidase alfa start were stratified by low (≤0.5 g/24 h) or high (>0.5 g/24 h) baseline proteinuria and by ‘classic’ or ‘non-classic’ phenotype. Overall, 193 male patients with low (n = 135) or high (n = 58) baseline proteinuria were evaluated. Compared with patients with low baseline proteinuria, those with high baseline proteinuria had a lower mean ± standard deviation baseline eGFR (89.1 ± 26.2 vs. 106.6 ± 21.8 mL/min/1.73 m2) and faster mean ± standard error eGFR decline (−3.62 ± 0.42 vs. −1.61 ± 0.28 mL/min/1.73 m2 per year; p < 0.0001). Patients with classic Fabry disease had similar rates of eGFR decline irrespective of baseline proteinuria; only one patient with non-classic Fabry disease had high baseline proteinuria, preventing meaningful comparisons between groups. In this analysis, baseline proteinuria significantly impacted the rate of eGFR decline in the overall population, suggesting that early treatment with good proteinuria control may be associated with renoprotective effects.

Metabolic Fingerprinting of Fabry Disease: Diagnostic and Prognostic Aspects

Fabry disease (FD) is an X-linked lysosomal disease due to a deficiency in the activity of the lysosomal-galactosidase A (GalA), a key enzyme in the glycosphingolipid degradation pathway. FD is a complex disease with a poor genotype–phenotype correlation. In the early stages, FD could involve the peripheral nervous system (acroparesthesias and dysautonomia) and the ski (angiokeratoma), but later kidney, heart or central nervous system impairment may significantly decrease life expectancy. The advent of omics technologies offers the possibility of a global, integrated and systemic approach well-suited for the exploration of this complex disease. In this narrative review, we will focus on the main metabolomic studies, which have underscored the importance of detecting biomarkers for a diagnostic and prognostic purpose in FD. These investigations are potentially useful to explain the wide clinical, biochemical and molecular heterogeneity found in FD patients. Moreover, the quantitative mass spectrometry methods developed to evaluate concentrations of these biomarkers in urine and plasma will be described. Finally, the complex metabolic biomarker profile depicted in FD patients will be reported, which varies according to gender, types of mutations, and therapeutic treatment.

Generation of an in vitro model for peripheral neuropathy in Fabry disease using CRISPR-Cas9 in the nociceptive dorsal root ganglion cell line 50B11

Fabry disease is a glycosphingolipid storage disorder that is caused by a genetic deficiency of the lysosomal enzyme alpha-galactosidase A (AGA, EC 3.2.1.22). As a result, the glycolipid substrate, globotriaosylceramide (Gb3) accumulates in various cell types throughout the body producing a multisystem disease that affects the vascular, cardiac, renal, and nervous systems. A hallmark of this disorder is neuropathic pain that occurs in up to 80% of Fabry patients and has been characterized as a small fiber neuropathy. The molecular mechanism by which changes in AGA activity produce neuropathic pain is not clear, in part due to a lack of relevant model systems. Using 50B11 cells, an immortalized dorsal root ganglion neuron with nociceptive characteristics derived from rat, we used CRISPR-Cas9 gene editing of the galactosidase alpha (GLA) gene for AGA to create two stable knock-out clones that have the phenotypic characteristics of Fabry cells. The cell lines show severely reduced lysosomal AGA activity in homogenates as well as impaired degradation of Gb3 in cultured cells. This phenotype is stable over long-term culture. Similar to the unedited 50B11 cell line, the clones differentiate in response to forskolin and extend neurites. Flow cytometry experiments demonstrate that the gene-edited cells express TRPV1 pain receptor at increased levels compared to control, suggesting a possible mechanism for increased pain sensitization in Fabry patients. Our 50B11 cell lines show phenotypic characteristics of Fabry disease and grow well under standard cell culture conditions. These cell lines can provide a convenient model system to help elucidate the molecular mechanism of pain in Fabry patients.

Newborn screening for Fabry disease in Oregon: Approaching the iceberg of A143T and variants of uncertain significance

Fabry disease newborn screening (NBS) has been ongoing in Oregon for over 41 months by first-tier enzyme quantitation and second-tier DNA testing. During that period the majority of abnormal referrals received (34/60) were for the presence of the controversial c.427G > A (p.Ala143Thr) aka A143T and the majority of non-A143T referrals were for other variants of uncertain significance (17/60) resulting in at least 32 infants with an inconclusive case outcome even after clinical evaluation and/or diagnostic testing. To date there has been no significant family history or onset of symptoms in individuals with an inconclusive outcome. Based on our experience, we have developed a framework for approaching A143T and other variants of uncertain clinical significance in an attempt to balance sensitivity with the unnecessary medicalization of healthy infants.

Fabry Disease in Slovakia: How the Situation Has Changed over 20 Years of Treatment

Fabry disease (FD, OMIM#301500) is a rare inborn error of the lysosomal enzyme α-galactosidase (α-Gal A, EC 3.2.1.22) and results in progressive substrate accumulation in tissues with a wide range of clinical presentations. Despite the X-linked inheritance, heterozygous females may also be affected. Hemizygous males are usually affected more severely, with an earlier manifestation of the symptoms. Rising awareness among health care professionals and more accessible diagnostics have positioned FD among the most-common inherited metabolic diseases in adults. An early and correct diagnosis of FD is crucial with a focus on personalised therapy. Preventing irreversible destruction of vital organs is the main goal of modern medicine. The aim of this study was to offer a complex report mapping the situation surrounding FD patients in Slovakia. A total of 48 patients (21 males, 27 females) with FD are registered in the Centre for Inborn Errors of Metabolism in Bratislava, Slovakia. In our cohort, we have identified three novel pathogenic variants in five patients. Three patients presented with the frameshift mutation c.736delA, and two others presented with the missense mutations c.203T>C, c.157A>C. Moreover, we present a new clinical picture of the pathogenic variant c.801+1G>A, which was previously described and associated with the renal phenotype.

High risk population screening for fabry disease in hemodialysis patients in Vojvodina

Introduction. Fabry disease (FD) is an X-linked lysosomal storage disease that develops as a consequence of mutation in the alpha-galactosidase A (GLA) gene. There are more than 1080 known variants in the GLA gene. Some of them are pathogenic, but most of them are benign or represent the genetic change that can be classified as a genetic variant of unknown significance or simply be a representation of genetic polymorphism. There are two main features of FD, classic form and late-onset variants of disease. The main target organs in patients with FD are kidneys, heart and nervous system. Bearing in mind the fact that FD is a rare disease, the best way for active searching of patients is high-risk population screening, after which family screening for every proband case should be performed. Methods. In this paper, we present results of a multicentric pilot study that represents findings from the screening of hemodialysis patients for FD in six hemodialysis units in Vojvodina. Results. We have found one patient with benign mutation and 16 patients with genetic polymorphisms in GLA gene. We have learned that genetic changes in GLA gene can be frequent, but very rarely are of clinical significance and lead to manifestations of FD. Conclusion. Results of this screening study will give us important insights into our future work

Challenging the traditional approach for interpreting genetic variants: Lessons from Fabry disease

Fabry disease (FD) is an X-linked genetic disease due to pathogenic variants in GLA. The phenotype varies depending on the GLA variant, alpha-galactosidase residual activity, patient's age and gender and, for females, X chromosome inactivation. Over 1000 variants have been identified, many through screening protocols more susceptible to disclose non-pathogenic variants or variants of unknown significance (VUS). This, together with the non-specificity of some FD symptoms, challenges physicians attempting to interpret GLA variants. The traditional way to interpreting pathogenicity is based on a combined approach using allele frequencies, genomic databases, global and disease-specific clinical databases, and in silico tools proposed by the American College of Medical Genetics and Genomics. Here, a panel of FD specialists convened to study how expertise may compare with the traditional approach. Several GLA VUS, highly controversial in the literature (p.Ser126Gly, p.Ala143Thr, p.Asp313Tyr), were re-analyzed through reviews of patients' charts. The same was done for pathogenic GLA variants with some specificities. Our data suggest that input of geneticists and physicians with wide expertise in disease phenotypes, prevalence, inheritance, biomarkers, alleles frequencies, disease-specific databases, and literature greatly contribute to a more accurate interpretation of the pathogenicity of variants, bringing a significant additional value over the traditional approach.

Detection of single nucleotide and copy number variants in the Fabry disease-associated GLA gene using nanopore sequencing

More than 900 variants have been described in the GLA gene. Some intronic variants and copy number variants in GLA can cause Fabry disease but will not be detected by classical Sanger sequence. We aimed to design and validate a method for sequencing the GLA gene using long-read Oxford Nanopore sequencing technology. Twelve Fabry patients were blindly analyzed, both by conventional Sanger sequence and by long-read sequencing of a 13 kb PCR amplicon. We used minimap2 to align the long-read data and Nanopolish and Sniffles to call variants. All the variants detected by Sanger (including a deep intronic variant) were also detected by long-read sequencing. One patient had a deletion that was not detected by Sanger sequencing but was detected by the new technology. Our long-read sequencing-based method was able to detect missense variants and an exonic deletion, with the added advantage of intronic analysis. It can be used as an efficient and cost-effective tool for screening and diagnosing Fabry disease.

Newborn Screening for Fabry Disease in Northeastern Italy: Results of Five Years of Experience

Fabry disease (FD) is a progressive multisystemic lysosomal storage disease. Early diagnosis by newborn screening (NBS) may allow for timely treatment, thus preventing future irreversible organ damage. We present the results of 5.5 years of NBS for FD by α-galactosidase A activity and globotriaosylsphingosine (lyso-Gb₃) assays in dried blood spot through a multiplexed MS/MS assay. Furthermore, we report our experience with long-term follow-up of positive subjects. We screened more than 170,000 newborns and 22 males were confirmed to have a GLA gene variant, with an incidence of 1:7879 newborns. All patients were diagnosed with a variant previously associated with the later-onset phenotype of FD or carried an unclassified variant (four patients) or the likely benign p.Ala143Thr variant. All were asymptomatic at the last visit. Although lyso-Gb₃ is not considered a reliable second tier test for newborn screening, it can simplify the screening algorithm when its levels are elevated at birth. After birth, plasma lyso-Gb₃ is a useful marker for non-invasive monitoring of all positive patients. Our study is the largest reported to date in Europe, and presents data from long-term NBS for FD that reveals the current incidence of FD in northeastern Italy. Our follow-up data describe the early disease course and the trend of plasma lyso-Gb₃ during early childhood.

Plasma Globotriaosylsphingosine and α-Galactosidase A Activity as a Combined Screening Biomarker for Fabry Disease in a Large Japanese Cohort

Fabry disease is an X-linked disorder of α-galactosidase A (GLA) deficiency. Our previous interim analysis (1 July 2014 to 31 December 2015) revealed plasma globotriaosylsphingosine as a promising primary screening biomarker for Fabry disease probands. Herein, we report the final results, including patients enrolled from 1 January to 31 December 2016 for evaluating the potential of plasma globotriaosylsphingosine and GLA activity as a combined screening marker. We screened 5691 patients (3439 males) referred from 237 Japanese specialty clinics based on clinical findings suggestive of Fabry disease using plasma globotriaosylsphingosine and GLA activity as primary screening markers, and GLA variant status as a secondary screening marker. Of the 14 males who tested positive in the globotriaosylsphingosine screen (≥2.0 ng/mL), 11 with low GLA activity (<4.0 nmol/h/mL) displayed GLA variants (four classic, seven late-onset) and one with normal GLA activity and no pathogenic variant displayed lamellar bodies in affected organs, indicating late-onset biopsy-proven Fabry disease. Of the 19 females who tested positive in the globotriaosylsphingosine screen, eight with low GLA activity displayed GLA variants (six classic, two late-onset) and five with normal GLA activity displayed a GLA variant (one classic) and no pathogenic variant (four late-onset biopsy-proven). The combination of plasma globotriaosylsphingosine and GLA activity can be a primary screening biomarker for classic, late-onset, and late-onset biopsy-proven Fabry disease probands.

Does administration of hydroxychloroquine/amiodarone accelerate accumulation of globotriaosylceramide and globotriaosylsphingosine in Fabry mice?

Drug-induced lysosomal storage disease (DILSD) caused by cationic amphiphilic drugs (CADs), which exhibits toxic manifestations and pathological findings mimicking Fabry disease (α-galactosidase A deficiency), has attracted the interests of clinicians and pathologists. Although the affected region is lysosomes in both the diseases, DILSD is characterized by intralysosomal accumulation of phospholipids and Fabry disease that of globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3). However, it is unknown whether administration of CADs affects the catabolism of Gb3 and Lyso-Gb3 in Fabry disease. In this study, we independently administered hydroxychloroquine/amiodarone to wild-type and Fabry mice and examined the effects of the drugs on the enzyme activity and substrates accumulated in organs and tissues. The results revealed that the administration of the drugs induced accumulation of phosphatidylcholine in both the wild-type and Fabry mice. However, reduction of α-galactosidase A activity in the organs and tissues of the wild-type mice was not found, and the storage of Gb3 and Lyso-Gb3 was not accelerated by these drugs in the Fabry mice. This suggests that hydroxychloroquine/amiodarone do not have any significant impact on the catabolism of Gb3 and Lyso-Gb3 in organs and tissues of both wild-type and Fabry mice.

•

Effects of cationic amphiphilic drugs on the catabolism of Gb3/Lyso-Gb3 were examined.

•

The drugs induced phospholipidosis in the wild-type and Fabry mice.

•

The drugs did not induce reduction of α-galactosidase A activity in the wild-type mice.

•

The drugs did not accelerate accumulation of Gb3/Lyso-gb3 in the Fabry mice.

Screening for Fabry disease in male patients with end-stage renal disease in western France

CONTEXT

Fabry disease is a rare X-linked genetic disease due to pathogenic variants in the GLA gene. Classic Fabry disease is characterized by glycosphingolipids accumulation in all organs including the kidney, resulting in end-stage renal disease in a subset of male patients. Fabry disease should therefore be considered in the differential diagnosis of patients with unexplained end-stage renal disease.

OBJECTIVE

We performed a prospective screening study in Western France to determine the prevalence of Fabry disease in a large population of dialyzed and transplanted patients.

PATIENTS AND METHODS

Patients meeting the inclusion criteria (males, 18-70 years with end-stage renal disease of unknown or vascular origin) were selected from the REIN® registry and the CRISTAL® database. Screening on filter papers was performed after patient consent was obtained during either a dialysis session or a transplantation follow-up visit.

RESULTS

One thousand five hundred and sixty-one end-stage renal disease male patients were screened and 819 consented (dialysis: n=242; transplant: n=577). One single patient was found with decreased alpha-galactosidase levels <25%. GLA sequencing identified the p.Phe113Leu variant in favor of an unknown superimposed kidney disease responsible for end-stage renal disease since this GLA pathogenic variant is associated with a later-onset cardiac form of Fabry disease with minimal kidney involvement. Family cascade genotyping revealed a previously undiagnosed affected brother.

CONCLUSION

The prevalence of Fabry disease in end-stage renal disease patients was 0.12%, questioning the efficacy of this screening strategy with respect to the low prevalence. However, beside the benefit for the patient and his family, the increased awareness of Fabry disease among participating nephrologists may be of interest for future patients.

Opinions of adults affected with later-onset lysosomal storage diseases regarding newborn screening: A qualitative study

Lysosomal storage diseases (LSDs) are a heterogeneous group of conditions causing substrate accumulation leading to progressive organ damage. Newborn screening (NBS) for several LSDs has become available in recent years due to advances in technology and treatment availability. While early initiation of treatment is lifesaving for those with infantile presentations, controversy continues regarding diagnosis of milder, later-onset diseases in infancy, including creation of pre-symptomatic populations of 'patients-in-waiting', the potential for medicalization, stigmatization, and/or discrimination. In-depth interviews were conducted with 36 adults [11 with Fabry disease (FD), 8 with Gaucher disease (GD), and 17 with late-onset Pompe disease (LOPD)], to determine their perspectives on NBS for their respective conditions. Thirty-four of 36 participants were in favor of NBS; both participants not in favor had GD1. Emergent themes influencing participants favorably toward NBS included earlier age of onset, a long diagnostic odyssey, less efficacious treatment, and the desire to have made different life decisions (e.g., relationships, career, or lifestyle) with the knowledge of their diagnosis. Concerns about insurance discrimination and psychological or physical burdens were associated with less favorable opinions of NBS. The ability for parents to make future reproductive decisions based their child's NBS result was considered favorably by some participants and unfavorably by others. Participants' specific condition (GD1, FD, or LOPD) contributed to these experiences differently. Participants with LOPD and FD favored NBS to initiate earlier treatment and prevent irreversible organ damage, whereas fewer patients with GD1 mentioned this benefit. Participants with LOPD had the longest diagnostic odyssey, while those with FD were more likely to report feeling misunderstood and experiencing accusations of malingering, both contributing to favorable views of NBS. Results expand prior quantitative findings by illuminating how participants' lived experiences can shape opinions about NBS. By understanding how currently affected individuals perceive the lifelong impact of a NBS result, genetic counselors can provide better anticipatory guidance to the parents of individuals diagnosed with a later-onset LSD by NBS.

The correlation of small fiber neuropathy with pain intensity and age in patients with Fabry's disease: A cross sectional study within a large Taiwanese family

Background

The relationships among small fiber neuropathy, age, sex and pain intensity in the context of Fabry's disease remain unclear. We aim to study the correlations of small fiber neuropathy, age, sex and pain intensity in Fabry patients.

Methods

We evaluated C-fiber function by recording the withdrawal latencies to painful heat stimulus (WLPHS) when each subject's right hand was immersed in a 50 °C hot water bath and correlated this parameter with the patient's perceived pain intensity and quality of life assessed by the short-form McGill Pain Questionnaire (SF-MPQ) in a large Taiwanese Fabry family and normal controls.

Results

Male Fabry patients showed a significantly increased WLPHS compared to that of normal controls. Furthermore, male Fabry patients showed a positive correlation of increased WLPHS with patient age. The SF-MPQ of male Fabry patients showed a bell distribution with age, and maximal pain scores were detected between the ages of the early 20s and late 40s. In contrast, the female Fabry patients had variable associations of WLPHS and SF-MPQ with age.

Conclusions

We proposed a probable mechanism by which globotriaosylceramide (Gb3) or globotriaosylsphingosine (lyso-Gb3) is gradually deposited into the small nerve bundles with increasing age, which induces continuous damage and produces injury discharges to sustain neuropathic pain in young male Fabry patients. However, once the small fibers are reduced to a certain degree, they no longer produce enough noxious discharges to sustain neuropathic pains in older male Fabry patients, which leads these patients to have lower SF-MPQ scores. In contrast, female Fabry patients had less and variable small fiber damage, pain intensity and clinical signs/symptoms.

Case Report: First Two Identified Cases of Fabry Disease in Central Asia

Background: Fabry disease (FD, OMIM #301500) is a rare, progressive, X-linked inherited, genetic disease due to the functional deficiency of lysosomal α-galactosidase (α-GAL) that leads to the accumulation of glycosphingolipids (mainly globotriaosylceramide or Gb₃) and its derivative globotriaosylsphingosine or lyso-Gb₃. Classic FD is a multisystem disorder which initially presents in childhood with neuropathic pain and dermatological, gastrointestinal, ocular, and cochleo-vestibular manifestations. Over time, end-organ damage such as renal failure, cardiac arrhythmia and early stroke may develop leading to reduced life expectancy in the absence of specific treatment. Case presentation: We describe two Kazakh patients who presented in adulthood with a delayed diagnosis. We conducted also a family screening through cascade genotyping. Conclusion: This is the first description of cases of Fabry disease in Central Asia. An extensive family pedigree enabled the identification of ten additional family members. Patients with rare genetic diseases often experience substantial delays in diagnosis due to their rarity and non-specific symptoms, which can negatively impact their management and delay treatment. FD may be difficult to diagnose because of the non-specificity of its early and later-onset symptoms and its X-linked inheritance. Raising awareness of clinicians is important for earlier diagnosis and optimal outcome of specific therapies.

The benefits and challenges of family genetic testing in rare genetic diseases-lessons from Fabry disease

Background

Family genetic testing of patients newly diagnosed with a rare genetic disease can improve early diagnosis of family members, allowing patients to receive disease‐specific therapies when available. Fabry disease, an X‐linked lysosomal storage disorder caused by pathogenic variants in GLA, can lead to end‐stage renal disease, cardiac arrhythmias, and stroke. Diagnostic delays are common due to the rarity of the disease and non‐specificity of early symptoms. Newborn screening and screening of at‐risk populations, (e.g., patients with hypertrophic cardiomyopathy or undiagnosed nephropathies) can identify individuals with Fabry disease. Subsequent cascade genotyping of family members may disclose a greater number of affected individuals, often at younger age than they would have been diagnosed otherwise.

Methods

We conducted a literature search to identify all published data on family genetic testing for Fabry disease, and discussed these data, experts’ own experiences with family genetic testing, and the barriers to this type of screening that are present in their respective countries.

Results

There are potential barriers that make implementation of family genetic testing challenging in some countries. These include associated costs and low awareness of its importance, and cultural and societal issues. Regionally, there are barriers associated with population educational levels, national geography and infrastructures, and a lack of medical geneticists.

Conclusion

In this review, the worldwide experience of an international group of experts of Fabry disease highlights the issues faced in the family genetic testing of patients affected with rare genetic diseases.

Gastrointestinal Involvement in Anderson-Fabry Disease: A Narrative Review

Anderson-Fabry disease (FD) is an X-linked lysosomal storage disorder leading to a wide array of clinical manifestations. Among these, gastrointestinal (GI) symptoms such as abdominal pain, bloating, and diarrhea affect about half of the FD adults and more than half of FD children. GI symptoms could be the first manifestation of FD; however, being non-specific, they overlap with the clinical picture of other conditions, such as irritable bowel syndrome and inflammatory bowel disease. This common overlap is the main reason why FD patients are often unrecognized and diagnosis is delayed for many years. The present narrative review is aimed to promote awareness of the GI manifestations of FD amongst general practitioners and specialists and highlight the latest findings of this rare condition including diagnostic tools and therapies. Finally, we will discuss some preliminary data on a patient presenting with GI symptoms who turned to be affected by a variant of uncertain significance of alpha-galactosidase (GLA) gene.

New mutation in Fabry disease: c.448delG, first phenotypic description

Fabry disease (FD) (Anderson-Fabry disease, OMIM 301500) is a genetic disorder caused by a pathogenic variant in the GLA gene on chromosome Xq22 that produces a deficiency in the lysosomal enzyme alpha-galactosidase A.

It is transmitted as an X-linked trait, although de novo mutations have been described. The objective of this report is to describe the clinical characteristics of a patient with FD who is a carrier of a mutation not previously studied, in order to provide information on the genotype-phenotype correlation in this pathology.

38-year-old patient who consulted Neurology for positional vertigo. He also reported acroparesthesia, anhidrosis, heat intolerance and episodes of abdominal pain, with postprandial discomfort from 10 years of age. Physical examination showed horizonto-rotatory nystagmus in both looks, the rest of the neurological evaluation did not present abnormalities. The presence of umbilical and thighs angiokeratomas was identified. Determination of Alpha-Galactosidase in blood was requested: 0.34 μmol/l/h (2.10–10.51 μmol/l/h). Genetic analysis detected a deletion of a guanine at position 448, in exon 3 of the GLA gene (c.448delG). This mutation was considered to be pathogenic, confirming the diagnosis of FD, although it is not described in the data bases. Genetic counseling and a family pedifree study were performed without finding relatives with this variant of the GLA gene or a family history of FD, which suggests a de novo mutation.

DNA methylation impact on Fabry disease

BACKGROUND

Fabry disease (FD) is a rare X-linked disease caused by mutations in GLA gene with consequent lysosomal accumulation of globotriaosylceramide (Gb3). Women with FD often show highly heterogeneous symptoms that can manifest from mild to severe phenotype.

MAIN BODY

The phenotypic variability of the clinical manifestations in heterozygous women with FD mainly depends on the degree and direction of inactivation of the X chromosome. Classical approaches to measure XCI skewness might be not sufficient to explain disease manifestation in women. In addition to unbalanced XCI, allele-specific DNA methylation at promoter of GLA gene may influence the expression levels of the mutated allele, thus impacting the onset and the outcome of FD. In this regard, analyses of DNA methylation at GLA promoter, performed by approaches allowing distinction between mutated and non-mutated allele, may be much more informative. The aim of this review is to critically evaluate recent literature articles addressing the potential role of DNA methylation in the context of FD. Although up to date relatively few works have addressed this point, reviewing all pertinent studies may help to evaluate the importance of DNA methylation analysis in FD and to develop new research and technologies aimed to predict whether the carrier females will develop symptoms.

CONCLUSIONS

Relatively few studies have addressed the complexity of DNA methylation landscape in FD that remains poorly investigated. The hope for the future is that ad hoc and ultradeep methylation analyses of GLA gene will provide epigenetic signatures able to predict whether pre-symptomatic female carriers will develop symptoms thus helping timely interventions.

Outcomes of Kidney Transplantation in Fabry Disease: A Meta-Analysis

Background: Fabry disease (FD) is a rare X-linked lysosomal storage disorder with progressive systemic deposition of globotriaosylceramide, leading to life-threatening cardiac, central nervous system, and kidney disease. Current therapy involves symptomatic medical management, enzyme replacement therapy (ERT), dialysis, kidney transplantation, and, more recently, gene therapy. The aim of this systematic review was to assess outcomes of kidney transplantation among patients with FD. Methods: A comprehensive literature review was conducted utilizing MEDLINE, EMBASE, and Cochrane Database, from inception through to 28 February 2020, to identify studies that evaluate outcomes of kidney transplantation including patient and allograft survival among kidney transplant patients with FD. Effect estimates from each study were extracted and combined using the random-effects generic inverse variance method of DerSimonian and Laird. Results: In total, 11 studies, including 424 kidney transplant recipients with FD, were enrolled. The post-transplant median follow-up time ranged from 3 to 11.5 years. Overall, the pooled estimated rates of all-cause graft failure, graft failure before death, and allograft rejection were 32.5% (95%CI: 23.9%–42.5%), 14.5% (95%CI: 8.4%–23.7%), and 20.2% (95%CI: 15.4%–25.9%), respectively. In the sensitivity analysis, limited only to the recent studies (year 2001 or newer when ERT became available), the pooled estimated rates of all-cause graft failure, graft failure before death, and allograft rejection were 28.1% (95%CI: 20.5%–37.3%), 11.7% (95%CI: 8.4%–16.0%), and 20.2% (95%CI: 15.5%–26.0%), respectively. The pooled estimated rate of biopsy proven FD recurrence was 11.1% (95%CI: 3.6%–29.4%), respectively. There are no significant differences in the risks of all-cause graft failure (p = 0.10) or mortality (0.48) among recipients with vs. without FD. Conclusions: Despite possible FD recurrence after transplantation of 11.1%, allograft and patient survival are comparable among kidney transplant recipients with vs. without FD.

Fabry disease and COVID-19: international expert recommendations for management based on real-world experience

The rapid spread of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 has raised questions about Fabry disease (FD) as an independent risk factor for severe COVID-19 symptoms. Available real-world data on 22 patients from an international group of healthcare providers reveals that most patients with FD experience mild-to-moderate COVID-19 symptoms with an additional complication of Fabry pain crises and transient worsening of kidney function in some cases; however, two patients over the age of 55 years with renal or cardiac disease experienced critical COVID-19 complications. These outcomes support the theory that pre-existent tissue injury and inflammation may predispose patients with more advanced FD to a more severe course of COVID-19, while less advanced FD patients do not appear to be more susceptible than the general population. Given these observed risk factors, it is best to reinforce all recommended safety precautions for individuals with advanced FD. Diagnosis of FD should not preclude providing full therapeutic and organ support as needed for patients with FD and severe or critical COVID-19, although a FD-specific safety profile review should always be conducted prior to initiating COVID-19-specific therapies. Continued specific FD therapy with enzyme replacement therapy, chaperone therapy, dialysis, renin-angiotensin blockers or participation to clinical trials during the pandemic is recommended as FD progression will only increase susceptibility to infection. In order to compile outcome data and inform best practices, an international registry for patients affected by Fabry and infected by COVID-19 should be established.

Detection of novel Fabry disease-associated pathogenic variants in Japanese patients by newborn and high-risk screening

BACKGROUND

In Japan, newborn and high-risk screening for Fabry disease (FD), an inherited X-linked disorder caused by GLA mutations, using dried blood spots was initiated in 2006. In newborn screening, 599,711 newborns were screened by December 2018, and 57 newborns from 54 families with 26 FD-associated variants were detected. In high-risk screening, 18,235 individuals who had symptoms and/or a family history of FD were screened by March 2019, and 236 individuals from 143 families with 101 FD-associated variants were detected. Totally 3, 116 variants were detected; 41 of these were not registered in Fabry-database.org or ClinVar and 33 were definitely novel. Herein, we report the clinical outcomes and discuss the pathogenicity of the 41 variants.

METHODS

We traced nine newborns and 46 individuals with the 33 novel variants, and nine newborns and 10 individuals with eight other variants not registered in the FD database, and analyzed the information on symptoms, treatments, and outcomes.

RESULTS

Thirty-eight of the 46 individuals with the 33 novel variants showed symptoms and received enzyme-replacement therapy and/or chaperone treatment.

CONCLUSION

Delayed diagnosis should be avoided in patients with FD. Our results will help clinicians diagnose FD and determine the appropriate treatment for patients with these variants.

Improvement of gastrointestinal symptoms in a significant proportion of male patients with classic Fabry disease treated with agalsidase beta: A Fabry Registry analysis stratified by phenotype

Background

Fabry disease is an inherited disorder of glycolipid metabolism with progressive involvement of multiple organs, including the gastrointestinal tract, in classically affected male patients. Clinical presentations in males with later-onset Fabry phenotypes are more heterogeneous and largely dependent on the level of residual α-galactosidase A activity.

Methods

We assessed agalsidase beta treatment outcomes of gastrointestinal symptoms in adult males with classic or later-onset Fabry disease. Self-reports of abdominal pain and diarrhea ('present'/'not present' since previous assessment) at last clinical visit (≥0.5 year of follow-up) were compared with treatment-baseline.

Results

Classic male patients were considerably younger at first treatment than the fewer males with later-onset phenotypes (36 vs. ~47 years) and reported gastrointestinal symptoms more frequently at baseline (abdominal pain: 56% vs. 13%; diarrhea: 57% vs. 23%). As compared with baseline, significantly fewer classic patients reported abdominal pain after a median of 4.7 years of treatment (N = 171, 56% vs. 41%, P < 0.001). Moreover, significantly fewer patients reported diarrhea after 5.5 years of follow-up (N = 169, 57% vs. 47%, P < 0.05). Among the males with later-onset phenotypes, albeit statistically non-significant, abdominal pain reports reduced after a median of 4.2 years (N = 48, 13% vs. 4%) and diarrhea reports reduced after a median of 4.4 years of treatment (N = 47, 23% vs. 13%).

Conclusions

Sustained treatment with agalsidase beta was associated with improvement in abdominal pain and diarrhea in a significant proportion of classic male Fabry patients. Males with later-onset phenotypes reported gastrointestinal symptoms much less frequently at baseline as compared with classic patients, and non-significant reductions were observed.

Anti-drug antibody formation in Japanese Fabry patients following enzyme replacement therapy

Enzyme replacement therapy (ERT) for Fabry disease (deficiency of α-galactosidase A, α-Gal) with recombinant α-Gals (agalsidase alfa and agalsidase beta) is widely available and improves some of the clinical manifestations and biochemical findings. However, recent reports suggest that recurrent administration of recombinant enzymes often induces the formation of anti-drug antibodies, which may have a negative impact on the outcome of the therapy. We examined the formation of anti-drug antibodies using blood samples from 97 Japanese Fabry patients following ERT and tried to characterize them by means of enzyme-linked immunosorbent assay (ELISA), serum-mediated α-Gal inhibition, and immunochromatographic (IC) assay, followed by GLA gene analysis and measurement of plasma globotriaosylsphingosine (lyso-Gb3). ELISA revealed that 20/35 (57%) classic Fabry males were antibody (Immunoglobulin G, IgG) -positive (Ab+) at 6 months after the initiation of ERT, although only two of the seventeen (12%) later-onset Fabry males and none of the 45 Fabry females were. The Ab+ state was maintained at least until 24 months after the initiation of ERT in most of the cases, the exceptions being two patients who acquired immune tolerance during ERT. As many Ab+ patients have nonsense mutations, attention should be paid to the formation of anti-drug antibodies in Fabry patients harboring such gene mutations, who hardly produce α-Gal protein. Serum-mediated α-Gal inhibition was seen in most of the Ab+ patients and the antibodies affected the reduction of the plasma lyso-Gb3 level following ERT, suggesting that the antibodies inhibit the enzyme activity. There was a correlation between the results of the IC test and those of the ELISA. As the former is easy and rapid, it should be useful as a bed-side test.

•

The anti-drug antibodies formed in Fabry patients during ERT were characterized.

•

Serum-mediated α-Gal inhibition was seen in most of the antibody-positive patients.

•

The immunochromatographic test is easy, rapid, and useful as a bed-side test.