Phenotypic characteristics of the p.Asn215Ser (p.N215S) GLA mutation in male and female patients with Fabry disease: A multicenter Fabry Registry study

2024 Update of the TSOC Expert Consensus of Fabry Disease

As an X-linked inherited lysosomal storage disease that is caused by α-galactosidase A gene variants resulting in progressive accumulation of pathogenic glycosphingolipid (Gb3) accumulation in multiple tissues and organs, Fabry disease (FD) can be classified into classic or late-onset phenotypes. In classic phenotype patients, α-galactosidase A activity is absent or severely reduced, resulting in a more progressive disease course with multi-systemic involvement. Conversely, late-onset phenotype, often with missense variants (e.g., IVS4+919G>A) in Taiwan, may present with a more chronic clinical course with predominant cardiac involvement (cardiac subtype), as they tend to have residual enzyme activity, remaining asymptomatic or clinically silent during childhood and adolescence. In either form, cardiac hypertrophy remains the most common feature of cardiac involvement, potentially leading to myocardial fibrosis, arrhythmias, and heart failure. Diagnosis is established through α-galactosidase enzyme activity assessment or biomarker analyisis (globotriaosylsphingosine, Lyso-Gb3), advanced imaging modalities (echocardiography and cardiac magnetic resonance imaging), and genotyping to differentiate FD from other cardiomyopathy. Successful therapeutic response relies on early recognition and by disease awareness from typical features in classic phenotype and cardiac red flags in cardiac variants for timely therapeutic interventions. Recent advances in pharmacological approach including enzyme replacement therapy (agalsidase alfa or beta), oral chaperone therapy (migalastat), and substrate reduction therapy (venglustat) aim to prevent from irreversible organ damage. Genotype- and gender-based monitoring of treatment effects through biomarker (Lyso-Gb3), renal assessment, and cardiac responses using advanced imaging modalities are key steps to optimizing patient care in FD.

Plasma and platelet lipidome changes in Fabry disease

BACKGROUND

Fabry disease (FD) is an X-linked lysosomal storage disorder characterized by the progressive accumulation of globotriaosylceramide (Gb3) leading to systemic manifestations such as chronic kidney disease, cardiomyopathy, and stroke. There is still a need for novel markers for improved FD screening and prognosis. Moreover, the pathological mechanisms in FD, which also include systemic inflammation and fibrosis, are not yet fully understood.

METHODS

Plasma and platelets were obtained from 11 ERT (enzyme-replacement therapy)-treated symptomatic, 4 asymptomatic FD patients, and 13 healthy participants. A comprehensive targeted lipidomics analysis was conducted quantitating more than 550 lipid species.

RESULTS

Sphingadiene (18:2;O2)-containing sphingolipid species, including Gb3 and galabiosylceramide (Ga2), were significantly increased in FD patients. Plasma levels of lyso-dihexosylceramides, sphingoid base 1-phosphates (S1P), and GM3 ganglioside were also altered in FD patients, as well as specific plasma ceramide ratios used in cardiovascular disease risk prediction. Gb3 did not increase in patients' platelets but displayed a high inter-individual variability in patients and healthy participants. Platelets accumulated, however, lyso-Gb3, acylcarnitines, C16:0-sphingolipids, and S1P.

CONCLUSIONS

This study identified lipidome changes in plasma and platelets from FD patients, a possible involvement of platelets in FD, and potential new markers for screening and monitoring of this disease.

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.

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.

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.

Complex management of Fabry cardiomyopathy: a case report on the use of alcohol septal ablation and chaperone therapy

Background

Cardiac involvement in Fabry disease (FD) usually manifests as a concentric left ventricular hypertrophy with rare cases developing left ventricular outflow tract obstruction (LVOTO), symptoms varying from fatigue and exercise associated dyspnoea to angina or arrhythmias.

Case summary

We present the case of a 54-year-old man with cardiovascular risk factors and aggravated exertional dyspnoea in the past year, in whom the echocardiography showed hypertrophic obstructive cardiomyopathy (HOCM). Cardiac magnetic resonance was used as differential diagnosis tool between sarcomeric HOCM and other phenocopies, suggesting a cardiac involvement of FD. Final diagnosis was formulated based on genetic testing and enzymatic activity of α-galactosidase. Left ventricular outflow tract obstruction was addressed by alcohol septal ablation successfully both in short term as well as at 1-year follow-up.

Discussion

The present case illustrates the complex clinical pathway of a patient with HOCM due to FD, where multimodality imaging was instrumental from differential diagnosis to therapeutic choices, which addressed both the pathogenic background and the organ involvement. Although at the moment the number of patients with of FD cardiomyopathy undergoing LVOTO reduction therapies is scarce, current recommendations should be extended to also include these patients.

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.

The Diagnostic and Therapeutic Implications of Phenocopies and Mimics of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a common myocardial disease defined by increased left ventricular wall thickness unexplained by loading conditions. HCM frequently is caused by pathogenic variants in sarcomeric protein genes, but several other syndromic, metabolic, infiltrative, and neuromuscular diseases can result in HCM phenocopies. This review summarizes the current understanding of these HCM mimics, highlighting their importance across the life course. The central role of a comprehensive, multiparametric diagnostic approach and the potential of precision medicine in tailoring treatment strategies are emphasized.

Anderson-Fabry disease management: role of the cardiologist

Anderson-Fabry disease (AFD) is a lysosomal storage disorder characterized by glycolipid accumulation in cardiac cells, associated with a peculiar form of hypertrophic cardiomyopathy (HCM). Up to 1% of patients with a diagnosis of HCM indeed have AFD. With the availability of targeted therapies for sarcomeric HCM and its genocopies, a timely differential diagnosis is essential. Specifically, the therapeutic landscape for AFD is rapidly evolving and offers increasingly effective, disease-modifying treatment options. However, diagnosing AFD may be difficult, particularly in the non-classic phenotype with prominent or isolated cardiac involvement and no systemic red flags. For many AFD patients, the clinical journey from initial clinical manifestations to diagnosis and appropriate treatment remains challenging, due to late recognition or utter neglect. Consequently, late initiation of treatment results in an exacerbation of cardiac involvement, representing the main cause of morbidity and mortality, irrespective of gender. Optimal management of AFD patients requires a dedicated multidisciplinary team, in which the cardiologist plays a decisive role, ranging from the differential diagnosis to the prevention of complications and the evaluation of timing for disease-specific therapies. The present review aims to redefine the role of cardiologists across the main decision nodes in contemporary AFD clinical care and drug discovery.

Asn215Ser, Ala143Thr, and Arg112Cys variants in α-galactosidase A protein confer stability loss in Fabry's disease

Alpha galactosidase A (α-GalA) gene contains nine exons localized at the q-arm of the X chromosome. Generally, an α-GalA enzyme is involved in the removal of galactosyl moieties from the glycoproteins and glycolipids. Dysregulation results in the accumulation of glycoproteins as well as glycolipids in various organs leading to Fabry disease (FD). In this study, we examine the impact of Asn215Ser, Ala143Thr and Arg112Cys variants on the α-GalA protein structure contributing to functional dynamic changes in FD. The seven computational pathogenicity prediction methods were used to predict the effects of these variants on the α-GalA protein. The three-dimensional structure of α-GalA variants was modeled with the Swiss Model and Robetta server and validated using a variety of tools. Then, molecular dynamics (MD) simulation was performed to understand the stability and dynamic behavior of the wild-type and variants structures. Most of our analyzed pathogenicity prediction tools showed that Asn215Ser, Ala143Thr and Arg112Cys variants cause a deleterious effect on the α-GalA protein. Further, MD trajectory analysis showed the destabilizing effect of variants on α-GalA structure based on the root mean square deviation, root mean square fluctuation, solvent accessible surface area, the radius of gyration, hydrogen bond, cluster analysis and PCA analysis. This concludes that the presence of these variants could potentially affect the protein functional process of galactosyl moieties removal which might lead to Fabry disease.Communicated by Ramaswamy H. Sarma.

Interaction of Fabry Disease and Diabetes Mellitus: Suboptimal Recruitment of Kidney Protective Factors

Fabry disease is a lysosomal disease characterized by globotriaosylceramide (Gb3) accumulation. It may coexist with diabetes mellitus and both cause potentially lethal kidney end-organ damage. However, there is little information on their interaction with kidney disease. We have addressed the interaction between Fabry disease and diabetes in data mining of human kidney transcriptomics databases and in Fabry (Gla-/-) and wild type mice with or without streptozotocin-induced diabetes. Data mining was consistent with differential expression of genes encoding enzymes from the Gb3 metabolic pathway in human diabetic kidney disease, including upregulation of UGCG, the gene encoding the upstream and rate-limiting enzyme glucosyl ceramide synthase. Diabetic Fabry mice displayed the most severe kidney infiltration by F4/80+ macrophages, and a lower kidney expression of kidney protective genes (Pgc1α and Tfeb) than diabetic wild type mice, without a further increase in kidney fibrosis. Moreover, only diabetic Fabry mice developed kidney insufficiency and these mice with kidney insufficiency had a high expression of Ugcg. In conclusion, we found evidence of interaction between diabetes and Fabry disease that may increase the severity of the kidney phenotype through modulation of the Gb3 synthesis pathway and downregulation of kidney protective genes.

Fabry Disease Nephropathy: Histological Changes With Nonclassical Mutations and Genetic Variants of Unknown Significance

RATIONALE & OBJECTIVE

Fabry disease (FD) is an X-linked genetic disorder that causes lysosomal storage of glycosphingolipids, primarily globotriaosylceramide (Gb3) and its derivative globotriaosylsphingosine (lyso-Gb3), with multiorgan dysfunction including chronic kidney disease. Affected individuals may be carriers of gene variants that are of uncertain significance (GVUS). We describe kidney pathology at the early stages of FD-related kidney disease to gain insights into its association with GVUS and sex.

STUDY DESIGN

Single-center, case series.

SETTING & PARTICIPANTS

Thirty-five consecutively biopsied patients (aged 48.1±15.4 years, 22 females) from among 64 patients with genetically diagnosed FD. Biopsies were retrospectively screened using the International Study Group of Fabry Nephropathy Scoring System.

OBSERVATIONS

Genetic mutation type, p.N215S and D313Y, sex, age, estimated glomerular filtration rate (eGFR), plasma lyso-Gb3 (pLyso-Gb3) levels, and histological parameters, including Gb3 deposits were recorded. Genetic analyses showed mostly missense mutations, p.N215S variant in 15, and the "benign polymorphism" D313Y in 4 of the biopsied patients. Morphological lesions were similar for men and women except for interstitial fibrosis and arteriolar hyalinosis being more common in men. Early in their clinical course, patients with normal/mild albuminuria had podocyte, tubular, and peritubular capillary vacuoles/inclusions, and evidence of chronicity, i.e., glomerulosclerosis, interstitial fibrosis, tubular atrophy. These findings appeared to be associated with pLyso-Gb3, eGFR, and age.

LIMITATIONS

Retrospective design and inclusion of outpatients partially based on family pedigree.

CONCLUSIONS

In early stages of kidney disease in the setting of FD, numerous histological abnormalities are present. These observations suggest that kidney biopsies early in FD may reveal activity of kidney involvement that may inform clinical management.

Cluster analysis of kidney function decline among males with Fabry disease in a large United States electronic health records database

BACKGROUND

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by deficient α-galactosidase A activity. The spectrum of disease includes phenotypes ranging from "classic" to "later-onset," with varying kidney disease progression. Identifying patterns of declining kidney function and involvement of other major organs in patients with FD is important to guide therapy decisions.

METHODS

Clusters of patients with FD and similar estimated glomerular filtration rate (eGFR) decline and age were created using agglomerative clustering of data captured between 2007 and 2020 in the United States Optum Market Clarity database. Male patients with a diagnosis of FD and two or more eGFR values ≥6 months apart were included. Disease progression was compared with a control cohort of patients without an FD diagnosis.

RESULTS

eGFR values from 234 male patients with FD were analysed, yielding seven clusters. Five clusters demonstrated disease progression from "natural" eGFR decline, with a slight decrease in kidney function and eGFR usually within the normal range, to rapid, early decline in eGFR and cardiac complications. When compared with the control cohort, a more rapid decline and a higher percentage of cardiac hypertrophy, heart failure, arrhythmias and stroke were noted in the study group. An inflection point was observed in each cluster when deterioration of kidney function accelerated.

CONCLUSIONS

Clustering of male patients with FD by decline in kidney function, organ involvement and phenotype through analysis of real-world data provides a reference that could help determine the optimal time for initiation of FD-specific treatment and facilitate management decisions made by healthcare professionals.

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.

Advanced searching for hypertrophic cardiomyopathy heritability in real practice tomorrow

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease associated with morbidity and mortality at any age. As studies in recent decades have shown, the genetic architecture of HCM is quite complex both in the entire population and in each patient. In the rapidly advancing era of gene therapy, we have to provide a detailed molecular diagnosis to our patients to give them the chance for better and more personalized treatment. In addition to emphasizing the importance of genetic testing in routine practice, this review aims to discuss the possibility to go a step further and create an expanded genetic panel that contains not only variants in core genes but also new candidate genes, including those located in deep intron regions, as well as structural variations. It also highlights the benefits of calculating polygenic risk scores based on a combination of rare and common genetic variants for each patient and of using non-genetic HCM markers, such as microRNAs that can enhance stratification of risk for HCM in unselected populations alongside rare genetic variants and clinical factors. While this review is focusing on HCM, the discussed issues are relevant to other cardiomyopathies.

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.

An expert consensus on the recommendations for the use of biomarkers in Fabry disease

Fabry disease is an X-linked lysosomal storage disorder caused by the accumulation of glycosphingolipids in various tissues and body fluids, leading to progressive organ damage and life-threatening complications. Phenotypic classification is based on disease progression and severity and can be used to predict outcomes. Patients with a classic Fabry phenotype have little to no residual α-Gal A activity and have widespread organ involvement, whereas patients with a later-onset phenotype have residual α-Gal A activity and disease progression can be limited to a single organ, often the heart. Diagnosis and monitoring of patients with Fabry disease should therefore be individualized, and biomarkers are available to support with this. Disease-specific biomarkers are useful in the diagnosis of Fabry disease; non-disease-specific biomarkers may be useful to assess organ damage. For most biomarkers it can be challenging to prove they translate to differences in the risk of clinical events associated with Fabry disease. Therefore, careful monitoring of treatment outcomes and collection of prospective data in patients are needed. As we deepen our understanding of Fabry disease, it is important to regularly re-evaluate and appraise published evidence relating to biomarkers. In this article, we present the results of a literature review of evidence published between February 2017 and July 2020 on the impact of disease-specific treatment on biomarkers and provide an expert consensus on clinical recommendations for the use of those biomarkers.

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Early onset of nephrogenic diabetes insipidus due to fabry disease in a child with GLA N215S mutation: Case report and literature review

Background

Fabry disease (FD) is a rare X-linked lysosomal storage disorder. Renal involvement in FD is characterized by proteinuria and progressive renal decline. Reports on FD with nephrogenic diabetes insipidus as the initial manifestation are rare. In this paper, we report a pediatric case with an N215S variant.

Results

A boy with an onset of polydipsia and polyuria at approximately 4 years of age was diagnosed with nephrogenic diabetes insipidus. Whole-exome sequencing showed a GLA N215S variation with no secondary cause of diabetes insipidus. No family history of polydipsia or polyuria was reported; however, the patient's maternal grandmother and her two younger brothers had hypertrophic cardiomyopathy. Both brothers required surgery due to severe cardiac involvement, and the youngest brother died of heart disease at the age of 50 years. The patient's polydipsia and polyuria worsened over the next 7 years. Serum sodium was normal, but the patient required high-dose potassium chloride to maintain normal serum potassium levels. His physical and intellectual development was normal, with no common complications of nephrogenic diabetes insipidus, such as anemia, malnutrition, vomiting, high fever, or convulsions. Dried blood spot testing showed α-galactosidase A (α-gal A) activity of 0.6 μmol/L/h and a Lyso-GL-3 level of 7.01 ng/ml. The patient developed mild proteinuria and mild myocardial hypertrophy. Renal biopsy showed myeloid bodies and zebra bodies. After more than 1 year of ERT, his urine specific gravity increased to 1.005-1.008, which was a new sign reflecting the efficacy of ERT, although urine output was maintained at 3-5 ml/kg/hour. We will continue to monitor the patient's renal tubular function and urine output.

Conclusions

Nephrogenic diabetes insipidus may be the initial manifestation in children with FD and/or N215S variation. In FD, the same mutation in a family may present a completely different phenotype.

Clinical and CMR characteristics associated with cardiac events in patients with Fabry disease

BACKGROUND

The assessment of late gadolinium enhancement (LGE) and left ventricular hypertrophy (LVH) by cardiac magnetic resonance (CMR) as diagnostic and prognostic maker in Fabry disease is advancing. We aimed to investigate the impact of clinical characteristics and CMR findings on cardiac outcome in patients with FD.

METHODS

In this study 55 patients with genetically confirmed FD and available CMR imaging were included. The primary endpoint was defined as a composite of cardiac events including cardiac death, new occurrence of atrial fibrillation, heart failure, ventricular tachycardia and bradycardia requiring device insertion.

RESULTS

During a median follow-up of 4.9 years (IQR 3.7-5.9), 9 patients (16.3%) reached the primary cardiac end point. The global amount of LGE was associated with an increased risk for primary endpoint in the univariate analysis (HR 1.4 per 10% increase in LGE, p = 0.002). However maximal wall thickness (MWT) was the sole independent predictor of the primary endpoint in a stepwise logistic regression model (HR 9.8 per mm increase in MWT, p < 0.0001). Kaplan-Meier analysis revealed significant difference in event free survival rate between patients with and without LVH (Long-rank p = 0.006) and in patients with and without LGE (Long-rank p < 0.001). Patients without LVH and LGE were free of adverse cardiac events.

CONCLUSION

LVH and LGE detected by CMR were associated with adverse cardiac events in FD. In particular maximal wall thickness can be useful in cardiac risk stratification of FD patients.

Prevalence of Fabry disease-causing variants in the UK Biobank

BACKGROUND

Fabry disease is an X-linked lysosomal storage disorder resulting from deficiency of the alpha-galactosidase A enzyme leading to accumulation of globotriaosylceramide in multiple organ sites with prominent cardiovascular and renal involvement. Global prevalence estimates of Fabry disease based on clinical ascertainment range from 1 in 40 000 to 1 in 170 000. We aimed to determine the prevalence of Fabry disease-causing variants in UK Biobank.

METHODS

We sought GLA gene variants in exome sequencing data from 200 643 individuals from UK Biobank. We used ACMG/AMP guidelines (American College of Medical Genetics/Association for Molecular Pathology) to classify pathogenicity and compared baseline biomarker data, hospital ICD-10 (International Classification of Diseases version-10) codes, general practitioner records and self-reported health data with those without pathogenic variants.

RESULTS

We identified 81 GLA coding variants. We identified eight likely pathogenic variants on the basis of being rare (<1/10 000 individuals) and either previously reported to cause Fabry disease, or being protein-truncating variants. Thirty-six individuals carried one of these variants. In the UK Biobank, the prevalence of likely pathogenic Fabry disease-causing variants is 1/5732 for late-onset disease-causing variants and 1/200 643 for variants causing classic Fabry disease.

CONCLUSION

Fabry disease-causing GLA variants are more prevalent in an unselected population sample than the reported prevalence of Fabry disease. These are overwhelmingly variants associated with later onset. It is possible the prevalence of later-onset Fabry disease exceeds current estimates.

Patient reported quality of life and medication adherence in Fabry disease patients treated with migalastat: A prospective, multicenter study

AIMS

Chaperone therapy with migalastat is a novel therapy option in Fabry disease (FD). In contrast to biweekly intravenous enzyme-replacement-therapy in a healthcare setting, oral delivery of migalastat every other day relies on the patient self-administration. Therapy adherence to migalastat and patient reported outcomes have not yet been studied in a real-world scenario.

METHODS AND RESULTS

Prospective multicenter 'MigALastat Therapy Adherence among FABRY patients' (MALTA-FABRY) study examined therapy adherence and patient-reported outcomes including quality of life in FD-patients receiving migalastat. Outcome measurements were elicited by the 'Medication Adherence Questionnaire (MAQ)', 'SF-36' and 'Fabry Pain Questionnaire' over a follow-up period of 24 months. Therapy adherence was graded as high (MAQ score of 4), medium (score of 2-3) or low (score 0-1). Within the recruitment period between 2017 and 2021, 40 patients (19 females) from 3 German FD-centers were included in the study. Nearly all patients (n = 37, 92.5%) showed good therapy adherence (MAQ6M_mean:3.93, MAQ12M_mean:3.71 and MAQ24M_mean:3.7). Only one patient fulfilled criteria for low adherence. Patient reported outcomes with completed SF-36 questionnaires were available in 28 patients (14 females). Over 24 months, significant improvement of pain and life role limitations due to physical activity was reported (Pain: change from baseline: 8.57 points, 95%-CI: 1.32-15.82, p = 0.022; role limitations physical: change from baseline: 13.39 points, 95%-CI: 0.61-23.2, p = 0.048).

CONCLUSION

Migalastat therapy adherence in FD-patients was high and remained high over a follow-up period of 2 years. Patient reported quality of life remained mostly stable, while pain and physical limitations improved over time.

An Overview of Molecular Mechanisms in Fabry Disease

Fabry disease (FD) (OMIM #301500) is a rare genetic lysosomal storage disorder (LSD). LSDs are characterized by inappropriate lipid accumulation in lysosomes due to specific enzyme deficiencies. In FD, the defective enzyme is α-galactosidase A (α-Gal A), which is due to a mutation in the GLA gene on the X chromosome. The enzyme deficiency leads to a continuous deposition of neutral glycosphingolipids (globotriaosylceramide) in the lysosomes of numerous tissues and organs, including endothelial cells, smooth muscle cells, corneal epithelial cells, renal glomeruli and tubules, cardiac muscle and ganglion cells of the nervous system. This condition leads to progressive organ failure and premature death. The increasing understanding of FD, and LSD in general, has led in recent years to the introduction of enzyme replacement therapy (ERT), which aims to slow, if not halt, the progression of the metabolic disorder. In this review, we provide an overview of the main features of FD, focusing on its molecular mechanism and the role of biomarkers.

Nationwide screening of Fabry disease in patients with hypertrophic cardiomyopathy in Czech Republic

AIMS

Fabry disease (FD) is a rare X-linked genetic disorder caused by α-galactosidase A (AGALA) deficiency. Whereas 'classic' variant has multisystemic manifestation, the more recently described 'later-onset' variant is characterized by predominant cardiac involvement that often mimics hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

Consecutive unrelated patients with HCM were screened for FD in 16 (out of 17) cardiac centres in the Czech Republic covering specialized cardiology care from June 2017 to December 2018. AGALA activity and globotriaosylsphingosine (lyso-Gb₃ ) levels were measured in all subjects using the dry blood spot method. FD was suspected in male patients with AGALA activity <1.2 μmol/h/L and in females with either low AGALA activity or lyso-Gb₃  > 3.5 ng/mL. Positive screening results were confirmed by genetic testing. We evaluated 589 patients (390 males, 66%) with HCM (mean maximal myocardial thickness 19.1 ± 4.3 mm). The average age was 58.4 ± 14.7 years. In total, 17 patients (11 males, 6 females) had a positive screening result, and subsequently, six of them (four males and two females) had a genetically confirmed pathogenic GLA mutation (total prevalence of 1.02%). Five of these patients were carrying the p.N215S mutation known to cause a typical later-onset cardiac FD.

CONCLUSIONS

We confirmed the prevalence of FD repeatedly reported in previous screening programmes (approximately 1% irrespective of gender) in a non-selected HCM population in Central Europe. Our findings advocate a routine screening for FD in all adult patients with HCM phenotype including both genders. The dry blood spot method used led to identification of clearly pathogenic variants.

The Benefits of Family Screening in Rare Diseases: Genetic Testing Reveals 165 New Cases of Fabry Disease among At-Risk Family Members of 83 Index Patients

Background: Fabry disease (FD, OMIM #301500) is a rare, progressive, X-linked, inherited genetic disease caused by a functional deficiency of lysosomal α-galactosidase, leading to the accumulation of glycosphingolipids in virtually all of the body’s cell types and fluids. Patients with rare genetic diseases and non-specific symptoms often experience substantial diagnostic delays, which can negatively impact the prompt initiation of treatment. If FD is not treated specifically, end organ damage (such as chronic renal failure, hypertrophic cardiomyopathy with arrhythmia, and strokes) impairs quality of life and reduces life expectancy. Patients and Methods: For 83 consecutive patients with FD referred to the Russian reference center for lysosomal storage diseases, family trees were built and genetic testing (cascade genotyping) was offered to family members. Results: The pathogenic GLA variant associated with FD was identified for all 83 probands. Family testing using cascade genotyping enabled the identification of 165 additional cases of FD among the tested 331 at-risk family members. Discussion: This is the first study to have described family screening in a large Russian cohort of patients with FD and chronic kidney disease. Raising awareness of FD among clinicians is important for earlier diagnosis and specific treatment.

The Heart in Fabry Disease: Mechanisms Beyond Storage and Forthcoming Therapies

In patients with Fabry disease (FD), cardiovascular involvement is the main cause of death and reduction of quality of life. Left ventricular hypertrophy mimicking hypertrophic cardiomyopathy is the main feature of FD cardiac involvement although glycolipid storage occurs in all cardiac cellular types. Accumulation of lysosomal globotriasylceramide represents the main mechanism of cardiac damage in early stages, but secondary pathways of cellular and tissue damage, triggered by lysosomal storage, and including altered energy production, inflammation and cell death, contribute to cardiac damage and disease progression. These mechanisms appear prominent in more advanced stages, hampering and reducing the efficacy of FD-specific treatments. Therefore, additional cardiovascular therapies are important to manage cardiovascular symptoms and reduce cardiovascular events. Although new therapies targeting lysosomal storage are in development, a better definition and comprehension of the complex pathophysiology of cardiac damage in FD, may lead to identify new therapeutic targets beyond storage and new therapeutic strategies.

Cardiac Magnetic Resonance Features of Fabry Disease: From Early Diagnosis to Prognostic Stratification

In the past few years, the wide application of cardiac magnetic resonance (CMR) significantly changed the approach to the study of cardiac involvement in Fabry Disease (FD). The possibility to perform non-invasive tissue characterization, including new sequences such as T1/T2 mapping, offered a powerful tool for differential diagnosis with other forms of left ventricular hypertrophy. In patients with confirmed diagnosis of FD, CMR is the most sensitive non-invasive technique for early detection of cardiac involvement and it provides new insight into the evolution of cardiac damage, including gender-specific features. Finally, CMR multiparametric detection of subtle changes in cardiac morphology, function and tissue composition is potentially useful for monitoring the efficacy of specific treatment over time. This paper aims to provide a comprehensive review of current knowledge regarding the application of CMR in FD cardiac involvement and its clinical implication.

Relapsing minimal change disease superimposed on late-onset p.N215S Fabry nephropathy

We present the case of a 76-year-old man with late-onset Fabry disease caused by the p.N215S missense mutation, with Fabry cardiomyopathy and nephropathy. In this case, the diagnosis of Fabry disease was incidental and followed minimal change disease (MCD) onset, with nephrotic syndrome and acute kidney injury requiring renal replacement therapy. Fabry nephropathy associated with the p.N215S mutation is becoming increasingly recognized among older patients. The importance of electron microscopy is herein highlighted and histological features common to Fabry nephropathy and MCD are discussed, along with the challenges associated with the diagnosis and clinical management.

Fabry disease and kidney involvement: starting from childhood to understand the future

The accumulation of globotriaosylceramide (Gb-3) in multiple organs, such as the heart, kidney, and nervous system, due to mutations in the galactosidase alpha (GLA) gene, represents the key point of Fabry disease (FD). The common symptoms appear in childhood or adolescence, including neuropathic pain, angiokeratoma, acroparesthesia, and corneal opacities. A multi-organ involvement induces a significant deterioration in the quality of life with high mortality in adulthood. The accumulation of Gb-3 involves all types of kidney cells beginning at fetal development, many years before clinical manifestations. A decline in the glomerular filtration rate is rare in children, but it can occur during adolescence. Pediatric patients rarely undergo kidney biopsy that could assess the efficacy of enzyme replacement therapy (ERT) behind its diagnostic role. To date, diagnosis is achieved by detecting reduced α-Gal-A activity in leukocytes and plasma, allowing for the early start of ERT. This review focuses on pediatric kidney involvement in FD, analyzing in depth its diagnostic processes and treatment options.

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.

Migalastat Treatment in a Kidney-Transplanted Patient with Fabry Disease and N215S Mutation: The First Case Report

Fabry disease is a rare X-linked lysosomal storage disorder caused by mutations in the GLA gene, leading to deficient α-galactosidase A activity and, consequently, to glycosphingolipid accumulation in a wide variety of cells. Fabry disease due to N215S (c.644A>G, p.Asn215Ser) missense mutation usually results in a late-onset phenotype presenting with isolated cardiac involvement. We herein present the case of a patient with N215S mutation with cardiac involvement, namely left ventricular hypertrophy and ventricular arrhythmias, and end-stage renal disease requiring kidney transplantation. To the best of our knowledge, this is the first report of a kidney-transplanted Fabry patient treated with oral pharmacologic chaperone migalastat.

High-Risk Screening for Fabry Disease: A Nationwide Study in Japan and Literature Review

Fabry disease (FD) is an X-linked inherited disorder caused by mutations in the GLA gene, which encodes the lysosomal enzyme α-galactosidase A (α-Gal A). FD detection in patients at an early stage is essential to achieve sufficient treatment effects, and high-risk screening may be effective. Here, we performed high-risk screening for FD in Japan and showed that peripheral neurological manifestations are important in young patients with FD. Moreover, we reviewed the literature on high-risk screening in patients with renal, cardiac, and central neurological manifestations. Based on the results of this study and review of research abroad, we believe that FD can be detected more effectively by targeting individuals based on age. In recent years, the methods for high-risk screening have been ameliorated, and high-risk screening studies using GLA next-generation sequencing have been conducted. Considering the cost-effectiveness of screening, GLA sequencing should be performed in individuals with reduced α-Gal A activity and females with certain FD manifestations and/or a family history of FD. The findings suggest that family analysis would likely detect FD patients, although GLA sequencing of asymptomatic family members requires adequate genetic counseling.

Fabry Cardiomyopathy: Current Treatment and Future Options

Fabry disease is a multisystem X-linked lysosomal storage disorder caused by a mutation in the alpha-galactosidase A gene. Deficiency or reduced activity of alpha-galactosidase A (GLA) is leading to progressive intracellular accumulation of globotriaosylceramide (GL3) in various organs, including the heart, kidney and nerve system. Cardiac involvement is frequent and is evident as concentric left ventricular hypertrophy. Currently, the standard treatment is enzyme replacement therapy or chaperone therapy. However, early starting of therapy, before myocardial fibrosis has developed, is essential for long-term improvement of myocardial function. For future treatment options, various therapeutic approaches including gene therapy are under development. This review describes the current and potential future therapy options for Fabry cardiomyopathy.

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.

Human α-Galactosidase A Mutants: Priceless Tools to Develop Novel Therapies for Fabry Disease

Fabry disease (FD) is a lysosomal storage disease caused by mutations in the gene for the α-galactosidase A (GLA) enzyme. The absence of the enzyme or its activity results in the accumulation of glycosphingolipids, mainly globotriaosylceramide (Gb3), in different tissues, leading to a wide range of clinical manifestations. More than 1000 natural variants have been described in the GLA gene, most of them affecting proper protein folding and enzymatic activity. Currently, FD is treated by enzyme replacement therapy (ERT) or pharmacological chaperone therapy (PCT). However, as both approaches show specific drawbacks, new strategies (such as new forms of ERT, organ/cell transplant, substrate reduction therapy, or gene therapy) are under extensive study. In this review, we summarize GLA mutants described so far and discuss their putative application for the development of novel drugs for the treatment of FD. Unfavorable mutants with lower activities and stabilities than wild-type enzymes could serve as tools for the development of new pharmacological chaperones. On the other hand, GLA mutants showing improved enzymatic activity have been identified and produced in vitro. Such mutants could overcome several complications associated with current ERT, as lower-dose infusions of these mutants could achieve a therapeutic effect equivalent to that of the wild-type enzyme.

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.

Fabry disease pain: patient and preclinical parallels

ABSTRACT

Severe neuropathic pain is a hallmark of Fabry disease, a genetic disorder caused by a deficiency in lysosomal α-galactosidase A. Pain experienced by these patients significantly impacts their quality of life and ability to perform everyday tasks. Patients with Fabry disease suffer from peripheral neuropathy, sensory abnormalities, acute pain crises, and lifelong ongoing pain. Although treatment of pain through medication and enzyme replacement therapy exists, pain persists in many of these patients. Some has been learned in the past decades regarding clinical manifestations of pain in Fabry disease and the pathological effects of α-galactosidase A insufficiency in neurons. Still, it is unclear how pain and sensory abnormalities arise in patients with Fabry disease and how these can be targeted with therapeutics. Our knowledge is limited in part due to the lack of adequate preclinical models to study the disease. This review will detail the types of pain, sensory abnormalities, influence of demographics on pain, and current strategies to treat pain experienced by patients with Fabry disease. In addition, we discuss the current knowledge of Fabry pain pathogenesis and which aspects of the disease preclinical models accurately recapitulate. Understanding the commonalities and divergences between humans and preclinical models can be used to further interrogate mechanisms causing the pain and sensory abnormalities as well as advance development of the next generation of therapeutics to treat pain in patients with Fabry disease.

Hypertrophic Cardiomyopathy and Primary Restrictive Cardiomyopathy: Similarities, Differences and Phenocopies

Hypertrophic cardiomyopathy (HCM) and primary restrictive cardiomyopathy (RCM) have a similar genetic background as they are both caused mainly by variants in sarcomeric genes. These “sarcomeric cardiomyopathies” also share diastolic dysfunction as the prevalent pathophysiological mechanism. Starting from the observation that patients with HCM and primary RCM may coexist in the same family, a characteristic pathophysiological profile of HCM with restrictive physiology has been recently described and supports the hypothesis that familiar forms of primary RCM may represent a part of the phenotypic spectrum of HCM rather than a different genetic cardiomyopathy. To further complicate this scenario some infiltrative (amyloidosis) and storage diseases (Fabry disease and glycogen storage diseases) may show either a hypertrophic or restrictive phenotype according to left ventricular wall thickness and filling pattern. Establishing a correct etiological diagnosis among HCM, primary RCM, and hypertrophic or restrictive phenocopies is of paramount importance for cascade family screening and therapy.

Elevated Ambulatory Blood Pressure Measurements are Associated with a Progressive Form of Fabry Disease

 INTRODUCTION: Published data on hypertension incidence and management in Anderson-Fabry disease are scant and the contribution of elevated blood pressure to organ damage is not well recognized.

AIM

Therefore, we have assessed blood pressure values and their possible correlations with clinical findings in a well described cohort of Fabry patients.

METHODS

Between January 2015 and May 2019, all adult Fabry patients (n = 24 females, n = 8 males) referred to our institute were prospectively enrolled. During the first examination patient's genotype and clinical characteristics were recorded. Blood pressure data were obtained by standard observed office measurements followed, within 6 months, by ambulatory blood pressure monitoring and home self-recordings. Organ involvement, including kidneys, heart and brain, was monitored over time. Consequently, patients were defined as clinically stable or progressive through the Fabry Stabilization Index.

RESULTS

The standard office measurements have diagnosed hypertension in three (9.37%) patients, but the ambulatory monitoring showed elevated blood pressure in six (18.75%) patients, revealing three cases of masked hypertension. All the hypertensive patients were females and, compared with normotensive subjects, they presented a lower glomerular filtration rate (p < 0.05) and a more advanced cardiac hypertrophy (p < 0.05). Four (66.7%) of them were diagnosed with a progressive form of the disease through the Fabry Stabilization Index while the majority of the normotensive group (84.6%, n = 19) was stable over time. No correlation was found between the prevalence of hypertension and the type of mutations causing Fabry disease.

CONCLUSION

Hypertension can be found in a restricted portion of clinically stable Fabry patients. In contrast, patients presenting with a progressive organ involvement, particularly renal impairment, have a major risk of developing uncontrolled blood pressure, and should be followed carefully. Moreover, the ambulatory blood pressure monitoring proved to be useful to reveal masked hypertension, which can contribute to the progressive worsening of the organ damage. Therefore, a proper diagnosis and therapy of hypertension may improve the outcome of Fabry patients.

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.

Fabry Disease and the Heart: A Comprehensive Review

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by mutations of the GLA gene that result in a deficiency of the enzymatic activity of α-galactosidase A and consequent accumulation of glycosphingolipids in body fluids and lysosomes of the cells throughout the body. GB3 accumulation occurs in virtually all cardiac cells (cardiomyocytes, conduction system cells, fibroblasts, and endothelial and smooth muscle vascular cells), ultimately leading to ventricular hypertrophy and fibrosis, heart failure, valve disease, angina, dysrhythmias, cardiac conduction abnormalities, and sudden death. Despite available therapies and supportive treatment, cardiac involvement carries a major prognostic impact, representing the main cause of death in FD. In the last years, knowledge has substantially evolved on the pathophysiological mechanisms leading to cardiac damage, the natural history of cardiac manifestations, the late-onset phenotypes with predominant cardiac involvement, the early markers of cardiac damage, the role of multimodality cardiac imaging on the diagnosis, management and follow-up of Fabry patients, and the cardiac efficacy of available therapies. Herein, we provide a comprehensive and integrated review on the cardiac involvement of FD, at the pathophysiological, anatomopathological, laboratory, imaging, and clinical levels, as well as on the diagnosis and management of cardiac manifestations, their supportive treatment, and the cardiac efficacy of specific therapies, such as enzyme replacement therapy and migalastat.

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.

Narrative review on Morbus Fabry: diagnosis and management of cardiac manifestations

Fabry disease (FD) is an X-linked lysosomal storage disorder due to reduced or undetectable α-galactosidase A (AGAL-A) enzyme activity caused by pathogenic variants in the AGAL-A gene (GLA). Tissue and organ changes are caused by widespread progressive accumulation of globotriaosylceramide (Gb₃) and globotriaosylsphingosine (lysoGb₃). The classical form of FD is multisystemic with cutaneous (angiokeratomas), neurological (peripheral neuropathy, premature stroke), renal (proteinuria and renal insufficiency), and cardiac involvement. Later onset variants may be limited to the heart. The objective of this review is to summarize the current knowledge on cardiac manifestations of FD and effects of targeted therapy. Cardiac involvement is characterized by progressive hypertrophy, fibrosis, arrhythmias, heart failure and sudden cardiac death (SCD). Targeted therapy is based on enzyme replacement therapy (ERT). Recently, small molecular chaperone, migalastat, became available for patients carrying amenable pathogenic GLA variants. The management of cardiac complications requires a complex approach. Several measures differ from standard clinical guidelines. Betablockers should be used with caution due to bradycardia risk, amiodarone avoided if possible, and anticoagulation used from the first appearance of atrial fibrillation. In Fabry cardiomyopathy SCD calculators are inappropriate. The awareness of FD manifestations is essential for early identification of patients and timely treatment initiation.

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.

Cardiac Involvement in Fabry Disease: JACC Review Topic of the Week

Fabry disease (FD) is a rare X-linked inherited lysosomal storage disorder caused by deficient α-galactosidase A activity that leads to an accumulation of globotriasylceramide (Gb3) in affected tissues, including the heart. Cardiovascular involvement usually manifests as left ventricular hypertrophy, myocardial fibrosis, heart failure, and arrhythmias, which limit quality of life and represent the most common causes of death. Following the introduction of enzyme replacement therapy, early diagnosis and treatment have become essential to slow disease progression and prevent major cardiac complications. Recent advances in the understanding of FD pathophysiology suggest that in addition to Gb3 accumulation, other mechanisms contribute to the development of Fabry cardiomyopathy. Progress in imaging techniques have improved diagnosis and staging of FD-related cardiac disease, suggesting a central role for myocardial inflammation and setting the stage for further research. In addition, with the recent approval of oral chaperone therapy and new treatment developments, the FD-specific treatment landscape is rapidly evolving.

The Cardiovascular Phenotype in Fabry Disease: New Findings in the Research Field

Fabry disease (FD) is a lysosomal storage disorder, depending on defects in alpha-galactosidase A (GAL) activity. At the clinical level, FD shows a high phenotype variability. Among them, cardiovascular dysfunction is often recurrent or, in some cases, is the sole symptom (cardiac variant) representing the leading cause of death in Fabry patients. The existing therapies, besides specific symptomatic treatments, are mainly based on the restoration of GAL activity. Indeed, mutations of the galactosidase alpha gene (GLA) cause a reduction or lack of GAL activity leading to globotriaosylceramide (Gb3) accumulation in several organs. However, several other mechanisms are involved in FD’s development and progression that could become useful targets for therapeutics. This review discusses FD’s cardiovascular phenotype and the last findings on molecular mechanisms that accelerate cardiac cell damage.

Lyso-Gb3 Increases αvβ3 Integrin Gene Expression in Cultured Human Podocytes in Fabry Nephropathy

Background: Podocyturia in Fabry nephropathy leads to glomerulosclerosis and kidney disease progression. Integrins are involved in podocyte attachment to the glomerular basement membrane. We hypothesized that in Fabry nephropathy, lyso-Gb3 could modulate αvβ3 expression in podocytes. Together with UPAR, the αvβ3 integrin is a key mechanism involved in podocyte detachment and podocyturia. Methods: In cultured human podocytes stimulated with lyso-Gb3, the mRNA expression of the ITGAV and ITGB3 genes encoding integrins αv and β3, respectively, was analyzed by RT-qPCR. Results: In cultured human podocytes, lyso-Gb3 at concentrations encountered in the serum of Fabry patients increased ITGAV and ITGB3 mRNA levels within 3 to 6 h. This pattern of gene expression is similar to that previously observed for PLAUR (UPAR) gene expression but is in contrast to the delayed (24 h) upregulation of other markers of podocyte stress and mediators of injury, such as CD80, TGFβ1, CD74, Notch1, and HES. Conclusions: Human podocyte stress in response to glycolipid overload in Fabry nephropathy, exemplified by lyso-Gb3, is characterized by an early increase in the expression of components of the αvβ3/UPAR system, which contrasts with the delayed rise in the expression of other mediators of podocyte injury. This suggests that the αvβ3/UPAR system may be a therapeutic target in Fabry nephropathy.

Stratification of Fabry mutations in clinical practice: a closer look at α-galactosidase A-3D structure

BACKGROUND

Fabry disease (FD) is an X-linked lysosomal storage and multi-system disorder due to mutations in the α-galactosidase A (α-GalA) gene. We investigated the impact of individual amino acid exchanges in the α-GalA 3D-structure on the clinical phenotype of FD patients.

PATIENTS AND METHODS

We enrolled 80 adult FD patients with α-GalA missense mutations and stratified them into three groups based on the amino acid exchange location in the α-GalA 3D-structure: patients with active site mutations, buried mutations and other mutations. Patient subgroups were deep phenotyped for clinical and laboratory parameters and FD-specific treatment.

RESULTS

Patients with active site or buried mutations showed a severe phenotype with multi-organ involvement and early disease manifestation. Patients with other mutations had a milder phenotype with less organ impairment and later disease onset. α-GalA activity was lower in patients with active site or buried mutations than in those with other mutations (P < 0.01 in men; P < 0.05 in women) whilst lyso-Gb3 levels were higher (P < 0.01 in men; <0.05 in women).

CONCLUSIONS

The type of amino acid exchange location in the α-GalA 3D-structure determines disease severity and temporal course of symptom onset. Patient stratification using this parameter may become a useful tool in the management of FD patients.