Globotriaosylsphingosine (Lyso-Gb3) as a biomarker for cardiac variant (N215S) Fabry disease

Lysosomal Dysfunction: Connecting the Dots in the Landscape of Human Diseases

Lysosomes are the main organelles responsible for the degradation of macromolecules in eukaryotic cells. Beyond their fundamental role in degradation, lysosomes are involved in different physiological processes such as autophagy, nutrient sensing, and intracellular signaling. In some circumstances, lysosomal abnormalities underlie several human pathologies with different etiologies known as known as lysosomal storage disorders (LSDs). These disorders can result from deficiencies in primary lysosomal enzymes, dysfunction of lysosomal enzyme activators, alterations in modifiers that impact lysosomal function, or changes in membrane-associated proteins, among other factors. The clinical phenotype observed in affected patients hinges on the type and location of the accumulating substrate, influenced by genetic mutations and residual enzyme activity. In this context, the scientific community is dedicated to exploring potential therapeutic approaches, striving not only to extend lifespan but also to enhance the overall quality of life for individuals afflicted with LSDs. This review provides insights into lysosomal dysfunction from a molecular perspective, particularly in the context of human diseases, and highlights recent advancements and breakthroughs in this field.

Early Risk Stratification for Natural Disease Course in Fabry Patients Using Plasma Globotriaosylsphingosine Levels

BACKGROUND

Fabry disease is a very heterogeneous X-linked lysosomal storage disease. Disease manifestations in the kidneys, heart, and brain vary greatly, even between patients of the same sex and with the same disease classification (classical or nonclassical). A biomarker with a strong association with the development of disease manifestations is needed to determine the need for Fabry-specific treatment and appropriate frequency of follow-up because clinical manifestations of the disorder may take decennia to develop.

METHODS

We investigated the levels of plasma lysoGb3 levels over time and its association with disease manifestations and disease course in 237 untreated patients with Fabry disease (median age 42 years, 38% male) using linear mixed-effect models.

RESULTS

LysoGb3 levels are stable over time in plasma of untreated patients with Fabry disease. Higher levels of lysoGb3 were associated with steeper decline in eGFR ( P = 0.05) and a faster increase in albuminuria (measured as the urinary albumin-to-creatinine ratio, P < 0.001), left ventricular mass (measured on echocardiography, P < 0.001), left atrial volume index ( P = 0.003), and Fazekas score ( P = 0.003). In addition, regardless of age, higher lysoGb3 levels were associated with higher relative wall thickness ( P < 0.001) and unfavorable functional markers on echocardiography, including septal mitral annular early diastolic velocity (e', P < 0.001) and the ratio of early transmitral velocity (E) to e' (E/e', P = 0.001).

CONCLUSIONS

In an individual patient with Fabry disease, the plasma lysoGb3 level reached a specific level in early childhood which, in the absence of Fabry-specific treatment, remained stable throughout life. The level of lysoGb3 in untreated patients was associated with nearly all Fabry-specific disease manifestations, regardless of the sex of the patient.

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.

Late-onset fabry disease due to the p.Phe113Leu variant: the first italian cluster of five families

BACKGROUND

The GLA c.337T > C (p.Phe113Leu) is a known pathogenic variant associated to late-onset Fabry disease phenotype with predominant cardiac manifestations. A founder effect was demonstrated in a large cohort in the Portuguese region of Guimarães. Herein we report an in-depth phenotype description of a cluster of five Southern Italy families.

METHODS

Family pedigrees of five index males with the p.Phe113Leu variant were obtained and all at-risk relatives underwent biochemical and genetical screening test. Carriers of GLA p.Phe113Leu variant underwent subsequent multidisciplinary clinical and instrumental evaluation.

RESULTS

Thirty-one (16 M, 15 F) individuals with p.Phe113Leu pathogenic variant were identified. Sixteen out of 31 patients (51.6%) had cardiac manifestations. Notably, myocardial fibrosis was found in 7/8 patients, of whom 2 were under 40 years. Stroke occurred in 4 patients. White matter lesions were detected in 12/19 patients and occurred in 2/10 of subjects under 40 years. Seven females complained of acroparesthesias. Renal involvement occurred in 10 patients. Angiokeratomas were evident in 9 subjects. Eyes, ear, gastrointestinal and pulmonary involvement occurred in the minority of subjects.

CONCLUSION

This study demonstrates that a cluster of subjects with p.Phe113Leu pathogenic variant is also present in Southern Italy. Disease manifestations are frequent in both sexes and may occur early in life. Cardiac involvement represents the core manifestation, but neurological and renal involvement is also frequent, suggesting that extra-cardiac complications deserve clinical attention.

Optimizing human α-galactosidase for treatment of Fabry disease

Fabry disease is caused by a deficiency of α-galactosidase A (GLA) leading to the lysosomal accumulation of globotriaosylceramide (Gb3) and other glycosphingolipids. Fabry patients experience significant damage to the heart, kidney, and blood vessels that can be fatal. Here we apply directed evolution to generate more stable GLA variants as potential next generation treatments for Fabry disease. GLAv05 and GLAv09 were identified after screening more than 12,000 GLA variants through 8 rounds of directed evolution. Both GLAv05 and GLAv09 exhibit increased stability at both lysosomal and blood pH, stability to serum, and elevated enzyme activity in treated Fabry fibroblasts (19-fold) and GLA^-/- podocytes (10-fold). GLAv05 and GLAv09 show improved pharmacokinetics in mouse and non-human primates. In a Fabry mouse model, the optimized variants showed prolonged half-lives in serum and relevant tissues, and a decrease of accumulated Gb3 in heart and kidney. To explore the possibility of diminishing the immunogenic potential of rhGLA, amino acid residues in sequences predicted to bind MHC II were targeted in late rounds of GLAv09 directed evolution. An MHC II-associated peptide proteomics assay confirmed a reduction in displayed peptides for GLAv09. Collectively, our findings highlight the promise of using directed evolution to generate enzyme variants for more effective treatment of lysosomal storage diseases.

Metabolic Fingerprinting of Fabry Disease: Diagnostic and Prognostic Aspects

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

LC-MS lipidomics of renal biopsies for the diagnosis of Fabry disease

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Fabry is an X-linked lysosomal storage disease with deficiency in α-galactosidase.

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This deficiency results in the accumulation of glycosphinogolipids.

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Diagnosis is often made by analysis of globotriaosylceramide in fluids and tissues.

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Fabry is often misdiagnosed in female patients due to residual enzyme activity.

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Lipidomics by LC-HRMS enables identification of new biomarkers in Fabry.

Introduction

Lipidomics analysis or lipid profiling is a system-based analysis of all lipids in a sample to provide a comprehensive understanding of lipids within a biological system. In the last few years, lipidomics has made it possible to better understand the metabolic processes associated with several rare disorders and proved to be a powerful tool for their clinical investigation. Fabry disease is a rare X-linked lysosomal storage disorder (LSD) caused by a deficiency in α-galactosidase A (α-GAL A). This deficiency results in the progressive accumulation of glycosphingolipids, mostly globotriaosylceramide (Gb₃), globotriaosylsphingosine (lyso-Gb₃), as well as galabiosylceramide (Ga₂) and their isoforms/analogs in the vascular endothelium, nerves, cardiomyocytes, renal glomerular podocytes, and biological fluids.

Objectives

The primary objective of this study was to evaluate lipidomic signatures in renal biopsies to help understand variations in Fabry disease markers that could be used in future diagnostic tests.

Methods

Lipidomic analysis was performed by ultra-high pressure liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS) on kidney biopsies that were left over after clinical pathology analysis to diagnose Fabry disease.

Results

We employed UHPLC-HRMS lipidomics analysis on the renal biopsy of a patient suspicious for Fabry disease. Our result confirmed α-GAL A enzyme activity declined in this patient since a Ga2-related lipid biomarker was substantially higher in the patient's renal tissue biopsy compared with two controls. This suggests this patient has a type of LSD that could be non-classical Fabry disease.

Conclusion

This study shows that lipidomics analysis is a valuable tool for rare disorder diagnosis, which can be conducted on leftover tissue samples without disrupting normal patient care.

Interstitial lung disease in lysosomal storage disorders

Lysosomes are intracellular organelles that are responsible for degrading and recycling macromolecules. Lysosomal storage diseases (LSDs) are a group of inherited diseases caused by mutations affecting genes that encode the function of the lysosomal enzymes. Three LSDs are associated with lung involvement and/or interstitial lung disease (ILD): Gaucher disease (GD); Niemann-Pick disease, also known as acid sphingomyelinase deficiency (ASMD); and Fabry disease (FD). In GD and in ASMD, analysis of bronchoalveolar lavage fluid and lung biopsy can be informative, showing foamy cells. In GD, ILD is rare. Enzyme replacement therapy (ERT) has been available since 1991 and has greatly changed the natural history of GD, with pulmonary failure and death reported before the ERT era. In ASMD, ILD is frequent and is usually associated with spleen enlargement, low platelet cell count and low level of high-density lipoprotein-cholesterol. Results of ERT are promising regarding preliminary results of olipudase alfa in paediatric and adult ASMD populations. The most frequent respiratory manifestation in FD is COPD-like symptoms regardless of smoking habit and dyspnoea due to congestive heart failure. Early diagnosis of these three LSDs is crucial to prevent irreversible organ damage. Early initiation of ERT can, at least in part, prevent organ failure.

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.

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.

[Fabry disease: A review]

Fabry disease is the second most frequent lysosomal storage disorder. It is a X-linked genetic disease secondary to alpha-galactosidase A enzyme deficiency. This is a progressive and systemic disease that affects both males and females. Classical symptoms and organ involvements are acral pain crisis, cornea verticillata, hypertrophic cardiomyopathy, stroke and chronic kidney disease with proteinuria. Nevertheless, organ damages can be missing or pauci-symptomatic and other common symptoms are poorly recognised, such as gastrointestinal or ear involvement. In classical Fabry disease, symptoms first appear during childhood or teenage in males, but later in females. Patients may have non-classical or late-onset Fabry disease with delayed manifestations or with single-organ involvement. Recognition of Fabry disease is important because treatments are available, but it may be challenging. Diagnosis is easy in males, with dosage of alpha-galactosidase A enzyme activity into leukocytes, but more difficult in females who can express normal residual activity. Other plasmatic biomarkers, such as lyso-globotriaosylceramide (lyso-Gb3), are interesting in females, but need to be associated with GLA gene analysis. In this review, we aimed at summarize the main clinical manifestations of Fabry disease and propose a practical algorithm to know how to diagnose this complex disease.

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.

When and How to Diagnose Fabry Disease in Clinical Pratice

Fabry disease is a frequent lysosomal storage disorder secondary to the deficiency of alpha-galactosidase A enzyme. This X-linked genetic disease realizes progressive and systemic manifestations that affect both male and female. Fabry disease may present as "classical", as "late-onset" or "non-classical" forms. Symptoms and organ involvements of classical Fabry disease are acral pain crisis, cornea verticillata, hypertrophic cardiomyopathy, stroke and chronic kidney disease with proteinuria. Other common symptoms are often poorly recognized, such as gastrointestinal or ear involvements. In classical Fabry disease, symptoms first appear during childhood or during teenage years in males, but later in females. Patients with non-classical or late-onset Fabry disease have delayed manifestations or a single-organ involvement. Diagnosis is therefore difficult when classical organ involvements are missing, in paucisymptomatic patients or in late-onset forms. Recognition of Fabry disease is important because effective treatments are available. They have to be prescribed early. In male, diagnosis is made with alpha-galactosidase A enzyme activity dosage in leukocyte, that is very low or null in classical forms and under 30 percent in late-onset forms. Diagnosis is more challenging in females who may express normal residual enzyme activity. Other plasmatic biomarkers, such as lyso-globotriaosylceramide are interesting, especially in females. In this review, we aimed to summarize main clinical manifestations of Fabry disease to know when to evoke Fabry disease and propose a practical diagnosis algorithm to know how to diagnose.

Novel biomarkers for lysosomal storage disorders: Metabolomic and proteomic approaches

Lysosomal storage disorders (LSDs) are characterized by the accumulation of specific disease substrates inside the lysosomes of various cells, eventually leading to the deterioration of cellular function and multisystem organ damage. With the continuous discovery and validation of novel and advanced therapies for most LSDs, there is an urgent need to discover more versatile and clinically relevant biomarkers. The utility of these biomarkers should ideally extend beyond the screening and diagnosis of LSDs to the evaluation of disease severity and monitoring of therapy. Metabolomic and proteomic approaches provide the means to the discovery and validation of such novel biomarkers. This is achieved mainly through the application of various mass spectrometric techniques to common and easily accessible biological samples, such as plasma, urine and dried blood spots. In this review, we tried to summarize the complexity of the lysosomal disorders phenotypes, their current diagnostic and therapeutic approaches, the various techniques supporting metabolomic and proteomic studies and finally we tried to explore the newly discovered biomarkers for most LSDs and their reported clinical values.

A Proteomics-Based Analysis Reveals Predictive Biological Patterns in Fabry Disease

Background: Fabry disease (FD) is an X-linked progressive lysosomal disease (LD) due to glycosphingolipid metabolism impairment. Currently, plasmatic globotriaosylsphingosine (LysoGb3) is used for disease diagnosis and monitoring. However, this biomarker is inconstantly increased in mild forms and in some female patients. Materials and Methods: We applied a targeted proteomic approach to explore disease-related biological patterns that might explain the disease pathophysiology. Forty proteins, involved mainly in inflammatory and angiogenesis processes, were assessed in 69 plasma samples retrieved from the French Fabry cohort (FFABRY) and from 83 healthy subjects. For predictive performance assessment, we also included other LD samples (Gaucher, Pompe and Niemann Pick C). Results: The study yielded four discriminant proteins that include three angiogenesis proteins (fibroblast growth factor 2 (FGF2), vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor C (VEGFC)) and one cytokine interleukin 7 (IL-7). A clear elevation of FGF2 and IL-7 concentrations was observed in FD compared to other LD samples. No correlation was observed between these proteins and globotriaosylsphingosine (LysoGb3). A significant correlation exists between IL-7 and residual enzyme activity in a non-classical phenotype. This highlights the orthogonal biological information yielded by these proteins that might help in stratifying Fabry patients. Conclusion: This work highlights the potential of using proteomics approaches in exploring FD and enhancing FD diagnosis and therapeutic monitoring performances.

Natural history of the late-onset phenotype of Fabry disease due to the p.F113L mutation

BACKGROUND

The common GLA gene mutation p.F113L causes late-onset phenotype of Fabry disease (FD) with predominant cardiac manifestations. A founder effect of FD due to this mutation was found in the Portuguese region of Guimarães. Our study aims to deepen the knowledge on the natural history of this late-onset variant.

METHODS

203 consecutive adult Fabry patients with p.F113L mutation (79 males; mean age 46 ± 18 years), from this region, were submitted at baseline to a predefined diagnostic protocol. The occurrence of FD manifestations was analyzed in each decade of age in both genders.

RESULTS

In males, left ventricular hypertrophy (40.2%) and late gadolinium enhancement (21.4%) arose over 30 years; heart failure (HF) (21.9%), ventricular tachycardia (8.9%) and conduction disorders over 40 years; and bifascicular (13.1%) and complete atrioventricular blocks (5.9%) beyond 50 years of age. Cardiac manifestations occurred more commonly and 1-2 decades earlier in males; their frequency increased with age. Septum and posterior wall thickness, LV mass, QRS interval duration and pro-BNP levels increased with age in both genders. Mean survival free from HF (64 ± 1 vs. 76 ± 2 years) and pacemaker (71 ± 2 vs. 86 ± 1 years) was higher in females (p < .001). Albuminuria A2/A3 (33.7%), brain white matter lesions (50.3%) and sensorineural deafness (44.7%) arose before 30 years of age in both genders, increasing with age. Renal failure and stroke were rare. Lysosomal inclusions were demonstrated in podocytes of patients with proteinuria.

CONCLUSION

This study improves the knowledge on natural history of late-onset variants of FD, carrying major impact on clinical decisions and guidelines.

Founder effect of Fabry disease due to p.F113L mutation: Clinical profile of a late-onset phenotype

BACKGROUND

Knowledge on clinical profiles of late-onset phenotypes of Fabry disease (FD) is essential to better define their natural history. Our study aims to demonstrate a founder effect of FD due to the GLA gene mutation c.337T>C (p.F113L) in the Portuguese region of Guimarães; and to characterize the clinical profile of this late-onset phenotype in a large cohort of genetically related adult patients, living in the same region.

METHODS AND RESULTS

FD screening was performed in 150 adult patients with hypertrophic cardiomyopathy (HCM) and found 25 Fabry patients (16.6%). The p.F113L mutation was found in 21 of them, leading to a genealogy study and haplotype analysis of the p.F113L patients. Genealogy research revealed a 12-generation family tree with a common ancestor to p.F113L patients, suggesting a founder effect that was supported by haplotype findings. Pedigree analysis was performed and 120 consecutive p.F113L patients underwent a predefined diagnostic evaluation of FD multiorgan involvement. This late-onset phenotype was characterized by common and/or potentially severe cardiac manifestations (left ventricular hypertrophy 40.8%, atrial fibrillation 5%, non-sustained ventricular tachycardia 12.5%, atrioventricular block 18.3%, bifascicular block 13.4%). Extracardiac manifestations included albuminuria>30 mg/24 h 36.1%, chronic kidney disease≥G3 7.6%, brain white matter lesions 54.4%, stroke 3.3%, sensorineural deafness 44.5%, cornea verticillata 13.9%. Plasma lyso-GB3 was undetectable in females, regardless of clinical manifestations.

CONCLUSION

A founder effect of FD due to p.F113L mutation was documented by genealogy and genetics in a Portuguese region. In this late-onset phenotype, although cardiac manifestations carry the highest prognostic impact, extracardiac involvement is common.

Multiple phenotypic domains of Fabry disease and their relevance for establishing genotype- phenotype correlations

Fabry disease (FD) is a rare X-linked glycosphingolipidosis resulting from deficient α-galactosidase A (AGAL) activity, caused by pathogenic mutations in the GLA gene. In males, the multisystemic involvement and the severity of tissue injury are critically dependent on the level of AGAL residual enzyme activity (REA) and on the metabolic load of the disease, but organ susceptibility to damage varies widely, with heart appearing as the most vulnerable to storage pathology, even with relatively high REA. The expression of FD can be conceived as a multidomain phenotype, where each of the component domains is the laboratory or clinical expression of the causative GLA mutation along a complex pathophysiologic cascade pathway. The AGAL enzyme activity is the most clinically useful marker of the protein phenotype. The metabolic phenotype and the pathologic phenotype are diverse expressions of the storage pathology, respectively, assessed by biochemical and histological/ultrastructural methods. The storage phenotypes are the direct consequences of enzyme deficiency and hence, together with the enzymatic phenotype, constitute the more specific diagnostic markers of FD. In the pathophysiology cascade, the clinical phenotypes are most distantly linked to the underlying genetic causation, being critically influenced by the patients’ gender and age, and modulated by the effects of variation in other genetic loci, of polygenic inheritance and of environmental risk factors. A major challenge in the clinical phenotyping of patients with FD is the differential diagnosis between its nonspecific, later-onset complications, particularly the cerebrovascular, cardiac and renal, and similar chronic illnesses that are common in the general population. Comprehensive phenotyping, whenever possible performed in hemizygous males, is therefore crucial for grading the severity of pathogenic GLA variants, to clarify the phenotypic correlations of hypomorphic alleles, to define benign polymorphisms, as well as to establish the pathogenicity of variants of uncertain significance.

Diagnosis and treatment of the cardiovascular consequences of Fabry disease

Fabry disease (FD) has been a diagnostic challenge since it was first recognized in 1898, with patients traditionally suffering from considerable delay before a diagnosis is made. Cardiac involvement is the current leading cause of death in FD. A combination of improved enzyme assays, availability of genetic profiling, together with more organized clinical services for rare diseases, has led to a rapid growth in the prevalence of FD. The earlier and more frequent diagnosis of asymptomatic individuals before development of the phenotype has focussed attention on early detection of organ involvement and closer monitoring of disease progression. The high cost of enzyme replacement therapy at a time of constraint within many health economies, moreover, has challenged clinicians to target treatment effectively. This article provides an outline of FD for the general physician and summarizes the aetiology and pathology of FD, the cardiovascular consequences thereof, modalities used in diagnosis and then discusses current indications for treatment, including pharmacotherapy and device implantation.

Improving metabolome coverage and data quality: advancing metabolomics and lipidomics for biomarker discovery

This Feature Article highlights some of the key challenges within the field of metabolomics and examines what role separation and analytical sciences can play to improve the use of metabolomics in biomarker discovery and personalized medicine. Recent progress in four key areas is highlighted: (i) improving metabolite coverage, (ii) developing accurate methods for unstable metabolites including in vivo global metabolomics methods, (iii) advancing inter-laboratory studies and reference materials and (iv) improving data quality, standardization and quality control of metabolomics studies.