Fabry Disease: prevalence of affected males and heterozygotes with pathogenic GLA mutations identified by screening renal, cardiac and stroke clinics, 1995-2017

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.

Prevalence of Fabry disease and GLA variants in young patients with acute stroke: The challenge to widen the screening. The Fabry-Stroke Italian Registry

BACKGROUND

Fabry disease (FD) is a treatable X-linked lysosomal storage disorder caused by GLA gene variants leading to alpha-galactosidase A deficiency. FD is a rare cause of stroke, and it is still controversial whether in stroke patients FD should be searched from the beginning or at the end of the diagnostic workup (in cryptogenic strokes).

METHODS

Fabry-Stroke Italian Registry is a prospective, multicentric screening involving 33 stroke units. FD was sought by measuring α-galactosidase A activity (males) and by genetic tests (males with reduced enzyme activity and females) in patients aged 18-60 years hospitalized for TIA, ischemic stroke, or intracerebral hemorrhage. We diagnosed FD in patients with 1) already known pathogenic GLA variants; 2) novel GLA variants if additional clinical, laboratory, or family-derived criteria were present.

RESULTS

Out of 1906 patients, we found a GLA variant in 15 (0.79%; 95%CI 0.44-1.29) with a certain FD diagnosis in 3 (0.16%; 95%CI 0.03-0.46) patients, none of whom had hemorrhage. We identified 1 novel pathogenic GLA variant. Ischemic stroke etiologies in carriers of GLA variants were: cardioaortic embolism (33%), small artery occlusion (27%), other causes (20%), and undetermined (20%). Mild severity, recurrence, previous TIA, acroparesthesias, hearing loss, and small artery occlusion were predictors of GLA variant.

CONCLUSION

In this large multicenter cohort the frequency of FD and GLA variants was consistent with previous reports. Limiting the screening for GLA variants to patients with cryptogenic stroke may miss up to 80% of diagnoses. Some easily recognizable clinical features could help select patients for FD screening.

Anderson-Fabry Disease: Red Flags for Early Diagnosis of Cardiac Involvement

Anderson-Fabry disease (AFD) is a lysosome storage disorder resulting from an X-linked inheritance of a mutation in the galactosidase A (GLA) gene encoding for the enzyme alpha-galactosidase A (α-GAL A). This mutation results in a deficiency or absence of α-GAL A activity, with a progressive intracellular deposition of glycosphingolipids leading to organ dysfunction and failure. Cardiac damage starts early in life, often occurring sub-clinically before overt cardiac symptoms. Left ventricular hypertrophy represents a common cardiac manifestation, albeit conduction system impairment, arrhythmias, and valvular abnormalities may also characterize AFD. Even in consideration of pleiotropic manifestation, diagnosis is often challenging. Thus, knowledge of cardiac and extracardiac diagnostic "red flags" is needed to guide a timely diagnosis. Indeed, considering its systemic involvement, a multidisciplinary approach may be helpful in discerning AFD-related cardiac disease. Beyond clinical pearls, a practical approach to assist clinicians in diagnosing AFD includes optimal management of biochemical tests, genetic tests, and cardiac biopsy. We extensively reviewed the current literature on AFD cardiomyopathy, focusing on cardiac "red flags" that may represent key diagnostic tools to establish a timely diagnosis. Furthermore, clinical findings to identify patients at higher risk of sudden death are also highlighted.

Outcomes and management of kidney transplant recipients with Fabry disease: a review

Fabry disease is an X-linked inheritable lysosomal storage disease caused by various mutations of the galactosidase α gene resulting in α-galactosidase deficiency. Chronic kidney disease (CKD) is one of the most significant consequences of Fabry disease, with risk of end-stage kidney disease (ESKD) in this population. Like for other patients with ESKD, kidney transplant is the optimal treatment for Fabry disease patients with ESKD. However, enzyme replacement therapy and newer Fabry disease treatments remain important to mitigate other end organ damage such as cardiomyopathy post transplantation. This review is a primer on Fabry disease, which examines the outcomes of disease in the context of kidney transplant prior to, and during, the enzyme replacement treatment era, medical treatment of kidney transplant recipients with Fabry disease, and progress in screening studies.

FDrisk: development of a validated risk assessment tool for Fabry disease utilizing electronic health record data

Purpose

Fabry disease (FD) is a rare, X-linked, lysosomal storage disease characterized by great variability in clinical presentation and progressive multisystemic organ damage. Lack of awareness of FD and frequent misdiagnoses cause long diagnostic delays. To address the urgent need for earlier diagnosis, we created an online, risk-assessment scoring tool, the FDrisk, for predicting an individual's risk for FD and prompting diagnostic testing and clinical evaluation.

Methods

Utilizing electronic health records, data were collected retrospectively from randomly selected, deidentified patients with FD treated at the Emory Lysosomal Storage Disease Center. Deidentified, negative controls were randomly selected from the Fabry Disease Diagnostic Testing and Education project database, a program within the American Association of Kidney Patients Center for Patient Education and Research. Diagnosis of FD was documented by evidence of a pathogenic variant in GLA and/or an abnormal level of leukocyte α-Gal A. Thirty characteristic clinical features of FD were initially identified and subsequently curated into 16 clinical covariates used as predictors for the risk of FD. An overall prediction model and two sex-specific prediction models were built. Two-hundred and sixty samples (130 cases, 130 controls) were used to train the risk prediction models. One-hundred and ninety-seven independent samples (30 cases, 167 controls) were used for testing model performance. Prediction accuracy was evaluated using a threshold of 0.5 to determine a predicted case vs. control.

Results

The overall risk prediction model demonstrated 80% sensitivity, 83.8% specificity, and positive predictive value of 47.1%. The male model demonstrated 75% sensitivity, 95.8% specificity, and positive predictive value of 75%. The female model demonstrated 83.3% sensitivity, 81.3% specificity, and positive predictive value of 45.5%. Patients with risk scores at or above 50% are categorized as "at risk" for FD and should be sent for diagnostic testing.

Conclusion

We have developed a statistical risk prediction model, the FDrisk, a validated, clinician-friendly, online, risk-assessment scoring tool for predicting an individual's risk for FD and prompting diagnostic testing and clinical evaluation. As an easily accessible, user-friendly scoring tool, we believe implementing the FDrisk will significantly decrease the time to diagnosis and allow earlier initiation of FD-specific therapy.

Prevalence of Fabry disease in patients with chronic kidney disease: A systematic review and meta-analysis

Fabry disease (FD) is an X-linked lysosomal storage disease caused by pathogenic variants in the GLA gene. It has a wide range of clinical manifestations, typically related to the specific underlying GLA variant. One of the main features of FD is kidney involvement; therefore, several studies have addressed the prevalence of FD in all types of patients with chronic kidney disease. We performed a systematic review and meta-analysis of screening studies in chronic kidney disease patients, including those on dialysis, had undergone a kidney transplantation, and those who did not receive kidney replacement therapy, and assessed the prevalence of pathogenic variants in these cohorts. Fifty-five studies were included, involving a total of 84,062 individuals. Of these, 251 cases were positive for FD; a third of the reported GLA variants were of a benign phenotype (37.8%), followed by classical phenotype (31.7%), late onset (15.5%), and of uncertain significance (14.7%). The overall prevalence among dialysis patients was 0.10% (CI95%, 0.06-0.15), 0.28% (CI95%, 0.06-0.15) among patients with kidney transplantation, and 0.17% (CI95%, 0.11-0.39) among those without kidney replacement therapy. Although the overall prevalence of FD is low in patients with kidney involvement, screening, especially in patients who have not yet undergone kidney replacement therapy, is important, in order to provide timely and effective treatment interventions, including disease modifying therapies. The prevalence of kidney involvement in females with Fabry Disease is lower but this should not lead to inadequate follow up. Further research is also needed on the impact of genetic variants of uncertain significance to elucidate their role in Fabry disease.

Fabry Disease: More than a Phenocopy of Hypertrophic Cardiomyopathy

Fabry disease (FD) is a genetic lysosomal storage disease with frequent cardiovascular involvement, whose presence is a major determinant of adverse clinical outcomes. As a potentially treatable cause of left ventricular hypertrophy (LVH) and heart failure with preserved ejection fraction, the early recognition of FD is crucial to initiate enzyme replacement therapy and improve long-term prognosis. Multimodality imaging plays a central role in the evaluation of patients with FD and helps in the differential diagnosis of other conditions presenting with LVH. In the present review, we explore the current applications of multimodality cardiac imaging, in particular echocardiography and cardiovascular magnetic resonance, in the diagnosis, prognostic assessment, and follow-up of patients with FD.

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 questionnaire survey on the diagnosis and treatment of Fabry nephropathy in clinical practice

BACKGROUND

Fabry nephropathy is characterized by a deficiency of lysosomal alpha-galactosidase A, which results in proteinuria and kidney disease. The ineffectiveness of enzyme replacement therapy (ERT) for severe kidney failure highlights the need for early detection and meaningful markers. However, because the diagnosis and treatment of Fabry disease can vary according to the expertise of physicians, we evaluated the opinions of Korean specialists.

METHODS

A questionnaire regarding the management of Fabry nephropathy was emailed to healthcare providers with the experience or ability to treat individuals with Fabry nephropathy.

RESULTS

Of the 70 experts who responded to the survey, 43 were nephrologists, and 64.3% of the respondents reported having treated patients with Fabry disease. Pediatricians are treating primarily patients with classic types of the disease, while nephrologists and cardiologists are treating more patients with variant types. Only 40.7% of non-nephrologists agreed that a kidney biopsy was required at the time of diagnosis, compared with 81.4% of nephrologists. Thirty-eight of 70 respondents (54.3%) reported measuring globotriaosylsphingosine (lyso-Gb3) as a biomarker. The most common period to measure lyso-Gb3 was at the time of diagnosis, followed by after ERT, before ERT, and at screening. For the stage at which ERT should begin, microalbuminuria and proteinuria were chosen by 51.8% and 28.6% of respondents, respectively.

CONCLUSION

Nephrologists are more likely to treat variant Fabry disease rather than classic cases, and they agree that ERT should be initiated early in Fabry nephropathy, using lyso-Gb3 as a biomarker.

Imaging cardiac hypertrophy in hypertrophic cardiomyopathy and its differential diagnosis

PURPOSE OF REVIEW

The aim of this study was to review imaging of myocardial hypertrophy in hypertrophic cardiomyopathy (HCM) and its phenocopies. The introduction of cardiac myosin inhibitors in HCM has emphasized the need for careful evaluation of the underlying cause of myocardial hypertrophy.

RECENT FINDINGS

Advances in imaging of myocardial hypertrophy have focused on improving precision, diagnosis, and predicting prognosis. From improved assessment of myocardial mass and function, to assessing myocardial fibrosis without the use of gadolinium, imaging continues to be the primary tool in understanding myocardial hypertrophy and its downstream effects. Advances in differentiating athlete's heart from HCM are noted, and the increasing rate of diagnosis in cardiac amyloidosis using noninvasive approaches is especially highlighted due to the implications on treatment approach. Finally, recent data on Fabry disease are shared as well as differentiating other phenocopies from HCM.

SUMMARY

Imaging hypertrophy in HCM and ruling out other phenocopies is central to the care of patients with HCM. This space will continue to rapidly evolve, as disease-modifying therapies are under investigation and being advanced to the clinic.

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.

Epidemiology of Fabry disease in patients in hemodialysis in the Madrid community

This study screened for Fabry disease (FD) in patients in hemodialysis (HD) in the region of Madrid (CAM) with a cross-sectional design to evaluate HD-prevalent patients, followed by a three-year period prospective design to analyze HD-incident patients.

INCLUSION CRITERIA

patients older than 18 years on HD in the CAM, excluding patients diagnosed with any other hereditary disease with renal involvement different from FD, that sign the Informed Consent (IC).

EXCLUSION CRITERIA

underaged patients or not agreeing or not being capable of signing the IC.

RESULTS

3470 patients were included, 63% males and with an average age of 67.9±9.7 years. 2357 were HD-prevalent patients and 1113 HD-incident patients. For HD-prevalent patients, average time in HD was 45.2 months (SD 51.3), in HD-incident patients proteinuria was present in 28.4%. There were no statistical differences in plasmatic alpha-galactosidase A (α-GAL-A) activity or Lyso-GL-3 values when comparing HD-prevalent and HD-incident populations and neither between males and females. A genetic study was performed in 87 patients (2.5% of patients): 60 male patients with decreased enzymatic activity and 27 female patients either with a decreased GLA activity, increased Lyso-Gl3 levels or both. The genetic variants identified were: p.Asp313Tyr (4 patients), p.Arg220Gln (3 patients) and M290I (1 patient). None of the identified variants is pathogenic.

CONCLUSIONS

76% of HD Centers of the CAM participated in the study. This is the first publication to describe the prevalence of FD in the HD-population of a region of Spain as well as its average α-GAL-A-activity and plasmatic Lyso-Gl3 levels. It is also the first study that combines a cross-sectional design with a prospective follow-up design. This study has not identified any FD patient.

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.

Management of Hypertension in Fabry Disease

Fabry disease (FD), a rare X-linked lysosomal storage disorder that depletes alpha-galactosidase A (α-GalA), is caused by mutations in the GLA gene. Diminished α-GalA enzyme activity results in the accumulation of Gb3 and lyso-Gb3. The pathophysiology of hypertension in FD is complex and unclear. The storage of Gb3 in arterial endothelial cells and smooth muscle cells is known to produce vascular injury by increasing oxidative stress and inflammatory cytokines as a primary pathophysiological mechanism. In addition, Fabry nephropathy developed, resulting in a decrease in kidney function and contributing to hypertension. The prevalence of hypertension in patients with FD was between 28.4% and 56%, whereas hypertension in patients with chronic kidney disease ranged between 33% and 79%. A study using 24-hour ambulatory blood pressure monitoring (ABPM) to measure blood pressure (BP) indicated a high prevalence of uncontrolled hypertension in FD. Thus, 24-hour ABPM ought to be considered for FD hypertension assessments. Appropriate treatment of hypertension is believed to reduce mortality in patients with FD caused by kidney disease, cardiovascular disease, and cerebrovascular disease because hypertension significantly impacts organ damage. Up to 70% of FD patients have been reported to have kidney involvement, and angiotensin-converting enzyme inhibitors and angiotensin receptor blockers prescribed for proteinuria are recommended as first-line therapy with antihypertensive drugs. In conclusion, hypertension should be controlled appropriately, given the different morbidity and mortality caused by significant organ involvement in FD patients.

Diagnosis and Management of Fabry Disease in High-Risk Renal Disease Patients in Taiwan: A Single Center Study

BACKGROUND

Fabry disease (FD) is an X-linked inborn error of lysosomal storage disorder, a deficiency in lysosomal hydrolase α-galactosidase A activity due to pathogenic variants in the GLA gene. Accumulation of globotriaosylceramide in multiple organs contributes to end-stage kidney disease, heart failure, and cerebrovascular accidents.

METHODS

We began the FD screening program by involving male patients older than 20 years of age who were on chronic dialysis, had a post-kidney transplantation, and were part of the Pre-End Stage Renal Disease Program in our hospital. α-galactosidase A activity was detected through an initial dried blood spots screen assay, followed by levels of lyso-globotriaosylceramide and sequencing of the GLA gene when screening patients with suspected FD to confirm their diagnosis.

RESULTS

A total of 1812 patients had been FD screened, with the prevalence of FD being approximately 0.16 % (3/1812) up until June 2022. Interestingly, we confirmed a family cluster (2 sons and their mother) of having the c.936+919G>A mutation (designated GLA IVS4) with hypertrophic cardiomyopathy in Taiwan and another with the mutation c.644A>G (p.Asn215Ser), a more common later-onset variant reported in people of European or North American descent. Two patients were confirmed with cardiomyopathy through a cardiac biopsy, with their cardiac function later reversed after enzyme replacement therapy.

CONCLUSIONS

The FD screening test detects chronic kidney disease due to an unknown etiology and prevents other organ complications. Early detection of FD is crucial for reversing target organ damage with enzyme replacement therapy.

Cardiac magnetic resonance in Fabry disease

Fabry disease (FD) is a rare X-linked inherited lysosomal storage disorder caused by deficient a-galactosidase A activity that leads to an accumulation of glycolipids, mainly globotriaosylceramide (Gb3) and globotriaosylsphingosine, in affected tissues, including the heart. Cardiovascular involvement usually manifests as left ventricular hypertrophy (LVH), myocardial fibrosis, heart failure, and arrhythmias, which limit the 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 in slowing down the disease progression and preventing 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 cardiac damage. FD cardiomyopathy is characterized by an earlier stage of glycosphingolipid accumulation and a later one of hypertrophy. Morphological and functional aspects are not specific in the echocardiographic evaluation of Anderson-Fabry disease. Cardiac magnetic resonance with tissue characterization capability is an accurate technique for the differential diagnosis of LVH. Progress in imaging techniques has improved the diagnosis and staging of FD-related cardiac disease: a decreased myocardial T1 value is specific of FD. Late gadolinium enhancement is typical of the later stage of cardiac involvement but as in other cardiomyopathy is also valuable to predict the outcome and cardiac response to therapy.

Coronary microvascular disease in hypertrophic and infiltrative cardiomyopathies

Pathologic hypertrophy of the cardiac muscle is a commonly encountered phenotype in clinical practice, associated with a variety of structural and non-structural diseases. Coronary microvascular disease is considered to play an important role in the natural history of this pathological phenotype. Non-invasive imaging modalities, most prominently positron emission tomography and cardiac magnetic resonance, have provided insights into the pathophysiological mechanisms of the interplay between hypertrophy and the coronary microvasculature. This article summarizes the current knowledge on coronary microvascular dysfunction in the most frequently encountered forms of pathologic hypertrophy.

Magnitude of the Potential Screening Gap for Fabry Disease in Manitoba: A Population-Based Retrospective Cohort Study

Background:

Fabry disease is a rare disorder caused by the deficient activity of α-galactosidase A (GLA) that often leads to organ damage. Fabry disease can be treated with enzyme replacement or pharmacological therapy, but due to its rarity and nonspecific manifestations, it often goes undiagnosed. Mass screening for Fabry disease is impractical; however, a targeted screening program for high-risk individuals may uncover previously unknown cases.

Objective:

Our objective was to use population-level administrative health databases to identify patients at high risk of Fabry disease.

Design:

Retrospective cohort study.

Setting:

Population-level health administrative databases housed at the Manitoba Centre for Health Policy.

Patients:

All residents of Manitoba, Canada, between 1998 and 2018.

Measurements:

We ascertained the evidence of GLA testing in a cohort of patients at high risk of Fabry disease.

Methods:

Individuals without a hospitalization or prescription indicative of Fabry disease were included if they had evidence of 1 of 4 high-risk conditions for Fabry disease: (1) ischemic stroke <45 years of age, (2) idiopathic hypertrophic cardiomyopathy, (3) proteinuric chronic kidney disease or kidney failure of unknown cause, or (4) peripheral neuropathy. Patients were excluded if they had known contributing factors to these high-risk conditions. Those who remained and had no prior GLA testing were assigned a 0% to 4.2% probability of having Fabry disease depending on their high-risk condition and sex.

Results:

After applying exclusion criteria, 1386 individuals were identified as having at least 1 high-risk clinical condition for Fabry disease in Manitoba. There were 416 GLA tests conducted during the study period, and of those, 22 were conducted in individuals with at least 1 high-risk condition. This leaves a screening gap of 1364 individuals with a high-risk clinical condition for Fabry disease in Manitoba who have not been tested. At the end of the study period, 932 of those individuals were still alive and residing in Manitoba, and if screened today, we expect between 3 and 18 would test positive for Fabry disease.

Limitations:

The algorithms we used to identify our patients have not been validated elsewhere. Diagnoses of Fabry disease, idiopathic hypertrophic cardiomyopathy, and peripheral neuropathy were only available via hospitalizations and not physician claims. We were only able to capture GLA testing processed through public laboratories. Patients identified to be at high risk of Fabry disease by the algorithm did not undergo GLA testing due to a clinical rationale that we were unable to capture.

Conclusions:

Administrative health databases may be a useful tool to identify patients at higher risk of Fabry disease or other rare conditions. Further directions include designing a program to screen high-risk individuals for Fabry disease as identified by our administrative data algorithms.

Genetic causes of heart failure with preserved ejection fraction: emerging pharmacological treatments

Heart failure with preserved ejection fraction (HFpEF) is a major driver of cardiac morbidity and mortality in developed countries, due to ageing populations and the increasing prevalence of comorbidities. While heart failure with reduced ejection fraction is dominated by left ventricular impairment, HFpEF results from a complex interplay of cardiac remodelling, peripheral circulation, and concomitant features including age, hypertension, obesity, and diabetes. In an important subset, however, HFpEF is subtended by specific diseases of the myocardium that are genetically determined, have distinct pathophysiology, and are increasingly amenable to targeted, innovative treatments. While each of these conditions is rare, they collectively represent a relevant subset within HFpEF cohorts, and their prompt recognition has major consequences for clinical practice, as access to dedicated, disease-specific treatments may radically change the quality of life and outcome. Furthermore, response to standard heart failure treatment will generally be modest for these individuals, whose inclusion in registries and trials may dilute the perceived efficacy of treatments targeting mainstream HFpEF. Finally, a better understanding of the molecular underpinnings of monogenic myocardial disease may help identify therapeutic targets and develop innovative treatments for selected HFpEF phenotypes of broader epidemiological relevance. The field of genetic cardiomyopathies is undergoing rapid transformation due to recent, groundbreaking advances in drug development, and deserves greater awareness within the heart failure community. The present review addressed existing and developing therapies for genetic causes of HFpEF, including hypertrophic cardiomyopathy, cardiac amyloidosis, and storage diseases, discussing their potential impact on management and their broader implications for our understanding of HFpEF at large.

Fabry Disease, a Rare Disorder with Cardiac Manifestations. The Problem of Diagnosis and Treatment: a Literature Review

Fabry disease (FD) is an X-linked lysosomal storage disease caused by a mutation in the gene encoding α-galactosidase A and leads to reduced activity or complete absence of this enzyme, which causes the accumulation of globotriaosylceramide (Gb3) and its deacylated form (lyso-Gb3) in cells of the whole body. FD can occur both with multisystem manifestations, including damage to the nervous system, kidneys, and skin, and can affect only the heart. Cardiac involvement is a major cause of poor quality of life and death in patients with FD and an underrecognized cause of heart failure with preserved ejection fraction and ventricular arrhythmias in men over 30 years of age and women over 40 years of age. Cardiac damage begins at an early age, progresses subclinically until the appearance of significant symptoms, and usually manifests as leftventricular hypertrophy, mimicking hypertrophic cardiomyopathy. After the introduction of enzyme replacement therapy, early recognition of FD and differential diagnosis with other causes of leftventricular hypertrophy have become crucial to limit the progression of the disease. Recent advances in the understanding of cardiac pathophysiology and imaging have improved diagnostic and therapeutic approaches to the cardiac manifestations of this pathology. Modern achievements in the study of cardiac manifestations of FD have made it possible to significantly improve diagnostic and therapeutic approaches, in particular, in relation to the identification of pathogenetic mechanisms of organ damage and early disruption of their function. A better understanding of secondary pathogenic pathways, such as myocardial inflammation, may influence future therapeutic strategies and timely diagnosis of FD. Delay in diagnosis and untimely initiation of treatment remain critical problems for many patients with FD, especially for patients with late-onset cardiovascular manifestations, in whom treatment effects may be more limited and ineffective. Cooperation between specialists in genetic diseases and cardiologists remains important to identify patients before the appearance of cardiac symptoms in order to obtain maximum therapeutic effects.

Screening for Fabry disease in Argentina in male patients with chronic kidney disease at all stages

We report three patients diagnosed with Fabry disease through a screening study which included individuals suffering from chronic kidney disease (CKD) at any stage. The study recruited 1740 male patients, and three Fabry patients were diagnosed, resulting in a frequency of 0.17%. The analysis by CKD stage group revealed frequencies of 3.03%, 0.77% and 0.17%, in CKD1, CKD3 and CKD5, respectively. Pedigree analysis was carried out for these families, with a high ratio index: pedigree (1:16). This study underlines the importance of considering Fabry disease in the differential diagnosis at every stage of CKD, including the early ones, and stresses the possibility of finding patients with late onset phenotypes.

Systematic cascade screening in the Danish Fabry Disease Centre: 20 years of a national single-centre experience

The lysosomal storage disorder Fabry disease is caused by deficient or absent activity of the GLA gene enzyme α-galactosidase A. In the present study we present the molecular and biochemical data of the Danish Fabry cohort and report 20 years' (2001-2020) experience in cascade genetic screening at the Danish National Fabry Disease Center. The Danish Fabry cohort consisted of 26 families, 18 index patients (9 males and 9 females, no available data for 8 index-patients) and 97 family members with a pathogenic GLA variant identified by cascade genetic testing (30 males and 67 females). Fourteen patients (5 males and 9 females; mean age of death 47.0 and 64.8 years respectively) died during follow-up. The completeness of the Fabry patient identification in the country has resulted in a cohort of balanced genotypes according to gender (twice number of females compared to males), indicating that the cohort was not biased by referral, and further resulted in earlier diagnosis of the disease by a lower age at diagnosis in family members compared to index-patients (mean age at diagnosis: index-patients 42.2 vs. family members 26.0 years). Six previously unreported disease-causing variants in the GLA gene were discovered. The nationwide screening and registration of Fabry disease families provide a unique possibility to establish a complete cohort of Fabry patients and to advance current knowledge of this inherited rare lysosomal storage disorder.

Beyond Sarcomeric Hypertrophic Cardiomyopathy: How to Diagnose and Manage Phenocopies

PURPOSE OF REVIEW

We describe the most common phenocopies of hypertrophic cardiomyopathy, their pathogenesis, and clinical presentation highlighting similarities and differences. We also suggest a step-by-step diagnostic work-up that can guide in differential diagnosis and management.

RECENT FINDINGS

In the last years, a wider application of genetic testing and the advances in cardiac imaging have significantly changed the diagnostic approach to HCM phenocopies. Different prognosis and management, with an increasing availability of disease-specific therapies, make differential diagnosis mandatory. The HCM phenotype can be the cardiac manifestation of different inherited and acquired disorders presenting different etiology, prognosis, and treatment. Differential diagnosis requires a cardiomyopathic mindset allowing to recognize red flags throughout the diagnostic work-up starting from clinical and family history and ending with advanced imaging and genetic testing. Different prognosis and management, with an increasing availability of disease-specific therapies make differential diagnosis mandatory.

Restrictive cardiomyopathy: definition and diagnosis

Restrictive cardiomyopathy (RCM) is a heterogeneous group of diseases characterized by restrictive left ventricular pathophysiology, i.e. a rapid rise in ventricular pressure with only small increases in filling volume due to increased myocardial stiffness. More precisely, the defining feature of RCM is the coexistence of persistent restrictive pathophysiology, diastolic dysfunction, non-dilated ventricles, and atrial dilatation, regardless of ventricular wall thickness and systolic function. Beyond this shared haemodynamic hallmark, the phenotypic spectrum of RCM is wide. The disorders manifesting as RCM may be classified according to four main disease mechanisms: (i) interstitial fibrosis and intrinsic myocardial dysfunction, (ii) infiltration of extracellular spaces, (iii) accumulation of storage material within cardiomyocytes, or (iv) endomyocardial fibrosis. Many disorders do not show restrictive pathophysiology throughout their natural history, but only at an initial stage (with an evolution towards a hypokinetic and dilated phenotype) or at a terminal stage (often progressing from a hypertrophic phenotype). Furthermore, elements of both hypertrophic and restrictive phenotypes may coexist in some patients, making the classification challenge. Restrictive pathophysiology can be demonstrated by cardiac catheterization or Doppler echocardiography. The specific conditions may usually be diagnosed based on clinical data, 12-lead electrocardiogram, echocardiography, nuclear medicine, or cardiovascular magnetic resonance, but further investigations may be needed, up to endomyocardial biopsy and genetic evaluation. The spectrum of therapies is also wide and heterogeneous, but disease-modifying treatments are available only for cardiac amyloidosis and, partially, for iron overload cardiomyopathy.

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 prevalence of Fabry disease among 1009 unrelated patients with hypertrophic cardiomyopathy: a Russian nationwide screening program using NGS technology

Background

There is a vast number of screening studies described in the literature from the beginning of the twenty-first century to the present day. Many of these studies are related to the estimation of Fabry disease (FD) morbidity among patients from high-risk groups, including adult patients with hypertrophic cardiomyopathy (HCM) and left ventricular hypertrophy (LVH). These studies show diverse detection frequencies (0–12%) depending on the methodology. Our study is the only example of large-scale selective FD screening based on the implementation of next-generation sequencing technology (NGS) as a first-level test to estimate FD morbidity in the Russian population over 18 years of age burdened with HCM.

Methods

The study included 1009 patients (578 males and 431 females), with a median age of 50 years, who were diagnosed with HCM according to current clinical guidelines. In the first stage of screening, all patients underwent molecular genetic testing (NGS method) of target regions. These regions included the coding sequences of 17 genes and mutations that can lead to the development of HCM. Lysosomal globotriaosylsphingosine (lyso-Gb3) concentrations and α-galactosidase A (α-gal A) enzyme activity were measured in the second stage of screening to reveal pathogenic or likely pathogenic variants in the GLA gene.

Results

We revealed 8 (0.8%) patients (3 (37.5%) males and 5 (62.5%) females) with an average age of 59 ± 13.3 years who had pathogenic, likely pathogenic variants and variants of uncertain significance (VUS) in the GLA gene (NM_000169.2) as a result of selective screening of 1009 Russian patients with HCM. FD was confirmed via biochemical tests in a male with the pathogenic variant c.902G > A, p.R301Q as well as in two females with likely pathogenic variants c.897C > A, p.D299E and c.1287_1288dup, p.*430Fext*?. These tests showed reduced enzymatic activity and increased substrate concentration. However, a female with the pathogenic variant c.416A > G, p.N139S and with normal enzymatic activity only had increased substrate concentrations. The revealed nucleotide variants and high values of biochemical indicators (lyso-Gb3) in these 4 patients allowed us to estimate the FD diagnosis among 1009 Russian patients with HCM. Mild extracardiac manifestations were observed in these four patients; however, both biochemical values within the reference range in females with the c.971T > G, p.L324W (VUS) variant. α-gal A activity and lyso-Gb3 concentrations were also within the normal range in two males with hemizygous variants, c.546T > C, p.D182D and c.640-794_640-791del (we regarded them as VUS), and in one female with the c.427G > A, p.A143T variant (with conflicting interpretations of pathogenicity).

Conclusion

The prevalence rate of FD among 1,009 adult Russian patients with HCM was 0.4%. We recommend FD screening among adult patients of both sexes with HCM and an undefined genetic cause via NGS method with subsequent analysis of α-gal A activity and lyso-Gb3 concentration in patients with pathogenic, likely pathogenic variants, and VUS. This strategy identifies patients with an atypical form of FD that is characterized by high residual activity of α-gal A, low concentrations of lyso-Gb3, and minor extracardiac manifestations.

The prevalence of Fabry disease in a statewide chronic kidney disease cohort - Outcomes of the aCQuiRE (Ckd.Qld fabRy Epidemiology) study

Background

Prevalence of Fabry disease amongst Chronic Kidney Disease (CKD) patients on haemodialysis has been shown to be approximately 0.2%.

Methods

We undertook a cross-sectional study employing a cascade screening strategy for Fabry Disease amongst 3000 adult, male and female patients affected by CKD stage 1-5D/T at public, specialty renal practices within participating Queensland Hospital and Health Services from October 2017 to August 2019. A multi-tiered FD screening strategy, utilising a combination of dried blood spot (DBS) enzymatic testing, and if low, then lyso-GB3 testing and DNA sequencing, was used.

Results

Mean (SD) age was 64.0 (15.8) years (n = 2992), and 57.9% were male. Eight participants withrew out of the 3000 who consented. Of 2992 screened, 6 (0.20%) received a diagnosis of FD, 2902 (96.99%) did not have FD, and 84 (2.81%) received inconclusive results. Of the patients diagnosed with FD, mean age was 48.5 years; 5 were male (0.29%) and 1 was female (0.08%); 4 were on kidney replacement therapy (2 dialysis and 2 transplant); 3 were new diagnoses.

Conclusions

Estimated overall FD prevalence was 0.20%. Screening of the broader CKD population may be beneficial in identifying cases of FD.

Trial registration

The aCQuiRE Study has been prospectively registered with the Queensland Health Database of Research Activity (DORA, https://dora.health.qld.gov.au) as pj09946 (Registered 3rd July 2017).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02805-8.

Brazilian consensus recommendations for the diagnosis, screening, and treatment of individuals with fabry disease: Committee for Rare Diseases - Brazilian Society of Nephrology/2021

Fabry disease (FD) is an X-linked inherited disorder caused by mutations in the GLA gene encoding enzyme alpha-galactosidase A (α-Gal A). The purpose of this study was to produce a consensus statement to standardize the recommendations concerning kidney involvement in FD and provide advice on the diagnosis, screening, and treatment of adult and pediatric patients. This consensus document was organized from an initiative led by the Committee for Rare Diseases (Comdora) of the Brazilian Society of Nephrology (SBN). The review considered randomized clinical trials, real-world data studies, and the expertise of its authors. The purpose of this consensus statement is to help manage patient and physician expectations concerning the outcomes of treatment. Our recommendations must be interpreted within the context of available evidence. The decisions pertaining to each individual case must be made with the involvement of patients and their families and take into account not only the potential cost of treatment, but also concurrent conditions and personal preferences. The Comdora intends to update these recommendations regularly so as to reflect recent literature evidence, real-world data, and appreciate the professional experience of those involved. This consensus document establishes clear criteria for the diagnosis of FD and for when to start or stop specific therapies or adjuvant measures, to thus advise the medical community and standardize clinical practice.

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.

Nationwide screening for Fabry disease in unselected stroke patients

Background and aims

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by disease-associated variants in the alpha-galactosidase A gene (GLA). FD is a known cause of stroke in younger patients. There are limited data on prevalence of FD and stroke risk in unselected stroke patients.

Methods

A prospective nationwide study including 35 (78%) of all 45 stroke centers and all consecutive stroke patients admitted during three months. Clinical data were collected in the RES-Q database. FD was diagnosed using dried blood spots in a stepwise manner: in males—enzymatic activity, globotriaosylsphingosine (lyso-Gb3) quantification, if positive followed by GLA gene sequencing; and in females GLA sequencing followed by lyso-Gb3.

Results

986 consecutive patients (54% men, mean age 70 years) were included. Observed stroke type was ischemic 79%, transient ischemic attack (TIA) 14%, intracerebral hemorrhage (ICH) 7%, subarachnoid hemorrhage 1% and cerebral venous thrombosis 0.1%. Two (0.2%, 95% CI 0.02–0.7) patients had a pathogenic variant associated with the classical FD phenotype (c.1235_1236delCT and p.G325S). Another fourteen (1.4%, 95% CI 0.08–2.4) patients had a variant of GLA gene considered benign (9 with p.D313Y, one p.A143T, one p.R118C, one p.V199A, one p.R30K and one p.R38G). The index stroke in two carriers of disease-associated variant was ischemic lacunar. In 14 carriers of GLA gene variants 11 strokes were ischemic, two TIA, and one ICH. Patients with positive as compared to negative GLA gene screening were younger (mean 60±SD, min, max, vs 70±SD, min, max, P = 0.02), otherwise there were no differences in other baseline variables.

Conclusions

The prevalence of FD in unselected adult patients with acute stroke is 0.2%. Both patients who had a pathogenic GLA gene variant were younger than 50 years. Our results support FD screening in patients that had a stroke event before 50 years of age.

Diagnosis and Management of Cardiovascular Involvement in Fabry Disease

Fabry disease (FD, OMIM 301500) is an X-linked lysosomal storage disease caused by pathogenic variants in the GLA gene. Cardiac involvement is common in FD and is responsible for impaired quality of life and premature death. The classic cardiac involvement is a nonobstructive form of hypertrophic cardiomyopathy, usually manifesting as concentric left ventricular hypertrophy, with subsequent arrhythmogenic intramural fibrosis. Treatment of patients with FD should be directed to prevent the disease progression to irreversible organ damage and organ failure. The aim of this review is to describe the current state of knowledge regarding cardiovascular involvement in FD, focusing on clinical and instrumental features, cardiovascular management, and targeted therapy.

Fabry-Stroke Italian Registry (FSIR): a nationwide, prospective, observational study about incidence and characteristics of Fabry-related stroke in young-adults. Presentation of the study protocol

Background

TIA and stroke, both ischemic and hemorrhagic, may complicate Fabry disease at young-adult age and be the first manifestation that comes to the clinician’s attention. No definite indications have yet been elaborated to guide neurologists in Fabry disease diagnostics. In current practice, it is usually sought in case of cryptogenic strokes (while Fabry-related strokes can also occur by classical pathogenic mechanisms) or through screening programs in young cerebrovascular populations. Data on recurrence and secondary prevention of Fabry’s stroke are scanty.

Methods

The study had a prospective observational design involving 33 Italian neurological Stroke Units. Considering the incidence of TIA/stroke in the European population aged < 60 years and the frequency of Fabry disease in this category (as foreseen by a pilot study held at the Careggi University-Hospital, Florence), we planned to screen for Fabry disease a total of 1740 < 60-year-old individuals hospitalized for TIA, ischemic, or hemorrhagic stroke. We investigated TIA and stroke pathogenesis through internationally validated scales and we gathered information on possible early signs of Fabry disease among all cerebrovascular patients. Every patient was tested for Fabry disease through dried blood spot analysis. Patients who received Fabry disease diagnosis underwent a 12-month follow-up to monitor stroke recurrence and multi-system progression after the cerebrovascular event.

Discussion

The potential implications of this study are as follows: (i) to add information about the yield of systematic screening for Fabry disease in a prospective large cohort of acute cerebrovascular patients; (ii) to deepen knowledge of clinical, pathophysiological, and prognostic characteristics of Fabry-related stroke.

Detailed Phenotype of GLA Variants Identified by the Nationwide Neurological Screening of Stroke Patients in the Czech Republic

Fabry disease (FD) is a rare X-linked disorder of glycosphingolipid metabolism caused by pathogenic variants within the alpha-galactosidase A (GLA) gene, often leading to neurological manifestations including stroke. Multiple screening programs seeking GLA variants among stroke survivors lacked detailed phenotype description, making the interpretation of the detected variant’s pathogenicity difficult. Here, we describe detailed clinical characteristics of GLA variant carriers identified by a nationwide stroke screening program in the Czech Republic. A total of 23 individuals with 8 different GLA variants were included in the study. A comprehensive diagnostic workup was performed by a team of FD specialists. The investigation led to the suggestion of phenotype reclassification for the G325S mutation from late-onset to classical. A novel variant R30K was found and was classified as a variant of unknown significance (VUS). The typical manifestation in our FD patients was a stroke occurring in the posterior circulation with an accompanying pathological finding in the cerebrospinal fluid. Moreover, we confirmed that cornea verticillata is typically associated with classical variants. Our findings underline the importance of detailed phenotype description and data sharing in the correct identification of pathogenicity of gene variants detected by high-risk-population screening programs.

Fabry Cardiomyopathy: Current Practice and Future Directions

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by mutations in the galactosidase A (GLA) gene that result in deficient galactosidase A enzyme and subsequent accumulation of glycosphingolipids throughout the body. The result is a multi-system disorder characterized by cutaneous, corneal, cardiac, renal, and neurological manifestations. Increased left ventricular wall thickness represents the predominant cardiac manifestation of FD. As the disease progresses, patients may develop arrhythmias, advanced conduction abnormalities, and heart failure. Cardiac biomarkers, point-of-care dried blood spot testing, and advanced imaging modalities including echocardiography with strain imaging and magnetic resonance imaging (MRI) with T1 mapping now allow us to detect Fabry cardiomyopathy much more effectively than in the past. While enzyme replacement therapy (ERT) has been the mainstay of treatment, several promising therapies are now in development, making early diagnosis of FD even more crucial. Ongoing initiatives involving artificial intelligence (AI)-empowered interpretation of echocardiographic images, point-of-care dried blood spot testing in the echocardiography laboratory, and widespread dissemination of point-of-care ultrasound devices to community practices to promote screening may lead to more timely diagnosis of FD. Fabry disease should no longer be considered a rare, untreatable disease, but one that can be effectively identified and treated at an early stage before the development of irreversible end-organ damage.

Rare inherited kidney diseases: an evolving field in Nephrology

There are more than 150 different rare genetic kidney diseases. They can be classified according to diagnostic findings as (i) disorders of growth and structure, (ii) glomerular diseases, (iii) tubular, and (iv) metabolic diseases. In recent years, there has been a shift of paradigm in this field. Molecular testing has become more accessible, our understanding of the underlying pathophysiologic mechanisms of these diseases has evolved, and new therapeutic strategies have become more available. Therefore, the role of nephrologists has progressively shifted from a mere spectator to an active player, part of a multidisciplinary team in the diagnosis and treatment of these disorders. This article provides an overview of the recent advances in rare hereditary kidney disorders by discussing the genetic aspects, clinical manifestations, diagnostic, and therapeutic approaches of some of these disorders, named familial focal and segmental glomerulosclerosis, tuberous sclerosis complex, Fabry nephropathy, and MYH-9 related disorder.

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.

[Chaperone molecules: The example of Fabry disease]

Fabry disease is due to mutations in the GLA gene that cause a deficiency of the activity of the lysosomal enzyme alpha-galactosidase A (α-gal A) resulting in intra-tissue accumulation of globotriaosylceramide. Recently, a novel therapeutic approach based on the pharmacological chaperone migalastat has been developed. It binds, in a specific and reversible manner, to the catalytic site of α-gal A mutants, to prevent their degradation by the quality control system of the endoplasmic reticulum and allow them to catabolize globotriaosylceramide in the lysosomes. This treatment concerns approximately 35% of the GLA gene mutations recognized as sensitive to migalastat according to an in vitro pharmacogenetic test. Two pivotal Phase III studies, FACETS: migalastat vs. placebo and ATTRACT: migalastat vs. enzyme replacement therapy analyzed the in vivo effects of migalastat. Despite some methodological limitations, promising results were found. Migalastat seems to be more effective than enzyme replacement therapy in reducing left ventricular mass index in case of cardiac hypertrophy and has comparable renal effects. This oral treatment is the first personalized treatment, based on the genetic profile of Fabry patients and opens a new era in the management of conformational diseases.

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.

Identification of patients with Fabry disease using routine pathology results: PATHFINDER (eGFR) study

AIMS

Lysosomal α-galactosidase A deficiency (Fabry disease (FD)) was considered an X-linked recessive disorder but is now viewed as a variable penetrance dominant trait. The prevalence of FD is 1 in 40 000-117 000 but the ascertainment of late-onset cases and degree of female penetrance makes this unclear. Its prevalence in the general population, especially in patients with abnormal renal function is unclear. This study attempted to identify the prevalence of FD in patients with abnormal renal function results from laboratory databases.

METHODS

Electronic laboratory databases were interrogated to identify from clinical biochemistry records patients with a phenotype of reduced estimated glomerular filtration rate categorised by age on one occasion or more over a 3-year time interval. Patients were recalled and a dried blood spot sample was collected for the determination of α-galactosidase A activity by fluorimetric enzyme assay in men and mass spectrometry assays of α-galactosidase A and lyso-globotriaosylceramide (lyso-GL-3) concentrations in women.

RESULTS

Samples were obtained from 1084 patients identified with reduced renal function. No cases of FD were identified in 505 men. From 579 women, one subject with reduced α-galactosidase activity (1.5 µmol/L/h) and increased Lyso-GL-3 (5.5 ng/mL) was identified and shown to be heterozygous for a likely FD pathogenic variant (GLA c.898C>T; p.L300F; Leu300Phe). It was later confirmed that she was a relative of a known affected patient.

CONCLUSIONS

Pathology databases hold routine information that can be used to identify patients with inherited errors of metabolism. Biochemical screening using reduced eGFR alone has a low yield for unidentified cases of Fabry Disease.

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.

Lyso-Gb3 associates with adverse long-term outcome in patients with Fabry disease

Background

Fabry disease (FD) is a rare X-linked lysosomal storage disease caused by mutations in the α-galactosidase A gene (GLA) leading to deficiency of α-galactosidase A and ultimately in progressive glycosphingolipid accumulation, especially globotriaosylceramide (Gb3) and its deacylated derivative globotriaosylsphingosine (Lyso-Gb3). The aim of the study was to assess plasma Lyso-Gb3 levels as a possible factor associated with adverse outcomes in FD.

Methods

In a cohort of 66 patients with genetically confirmed FD (26 males and 40 females), we analysed serum Lyso-Gb3 as a factor associated with adverse clinical outcomes in a long-term study. The main outcome was a composite endpoint of incident kidney replacement therapy, atrial fibrillation, pacemaker and/or implantable cardioverter defibrillator, cerebrovascular events or death, whichever occurred first.

Results

During the median follow-up time of 68 (40–80) months, events occurred in 19 (29%) of the patients. In a Cox multivariate regression analysis, Lyso-Gb3 levels (HR 4.62 (1.55 to 13.81); p=0.006) and the pretreatment exposure to Lyso-Gb3 (HR 3.41 (1.11 to 10.49); p=0.03) (both per SD increase) were significantly associated with adverse outcomes. If pretreatment Lyso-Gb3 exposure was added to multivariable logistic regression models containing age, sex, phenotype and enzyme replacement therapy as other covariates with the composite outcome as dependent variable, the area under the curve for the composite outcome significantly improved from 0.72 to 0.86 (p comparison=0.04).

Conclusion

Lyso-Gb3 is a significant risk factor associated with important clinical events. Whether treatment-related amelioration of Lyso-Gb3 levels will be associated with improved long-term outcome needs to be established in prospective intervention trials.

Renal Manifestations of Fabry Disease: A Narrative Review

Purpose of review

In this narrative review, we describe general aspects, histological alterations, treatment, and implications of Fabry disease (FD) nephropathy. This information should be used to guide physicians and patients in a shared decision-making process.

Source of information

Original peer-reviewed articles, review articles, and opinion pieces were identified from PubMed and Google Scholar databases. Only sources in English were accessed.

Methods

We performed a focused narrative review assessing the main aspects of FD nephropathy. The literature was critically analyzed from a theoretical and contextual perspective, and thematic analysis was performed.

Key findings

FD nephropathy is related to the progressive accumulation of GL3, which occurs in all types of renal cells. It is more prominent in podocytes, which seem to play an important role in the pathogenesis of this nephropathy. A precise detection of renal disorders is of fundamental importance because the specific treatment of FD is usually delayed, making reversibility unlikely and leading to a worse prognosis.

Limitations

As no formal tool was applied to assess the quality of the included studies, selection bias may have occurred. Nonetheless, we have attempted to provide a comprehensive review on the topic using current studies from experts in FD and extensive review of the literature.