Fabry Disease: Thirty-Five Mutations in the α-Galactosidase A Gene in Patients with Classic and Variant Phenotypes

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

Background

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

Methods

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

Results

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

Conclusions

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND AND OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Difficulties in Diagnosing Fabry Disease in Patients with Unexplained Left Ventricular Hypertrophy (LVH): Is the Novel GLA Gene Mutation a Pathogenic Mutation or Polymorphism?

Fabry disease (FD) is an X-linked, lysosomal glycosphingolipid storage disorder that occurs very rarely. Cardiac involvement may comprise of left ventricular hypertrophy (LVH), arrhythmias, conduction abnormalities, heart failure and valvular abnormalities. The goal of this study was to conduct gene analysis for FD in patients suffering from unexplained LVH. 120 patients over the age of 30 who were diagnosed by echocardiography with idiopathic LVH were included in the study. Patients with severe hypertension, intermediate valve disease such as moderate aortic stenosis, known FD, and a family history of autosomal dominant hypertrophic cardiomyopathy were excluded from the study. GLA gene mutations were studied by Sanger sequence analysis in all patients. Of the 120 total patients included in this study, 69 were female (58%) and 51 were male (42%). The mean age was 60.3 ± 15.7. GLA gene mutations were detected in three male patients. The detected mutations are as follows: NM_000169.2:IVS6-10G>A (c.1000-10G>A), NM_000169.2:c.937G>T (p.D313Y) (p.Asp313Tyr) and NM_000169.2:c.941A>T (p.K314M) (p.Lys314Met). Early diagnosis is of vital importance in FD, which can be treated with enzyme replacement. Genetic screening in patients diagnosed with idiopathic LVH by echocardiography is important in the early diagnosis and treatment of FD. Patients over 30 years of age with idiopathic LVH should be screened for FD. Various new polymorphisms can be detected in genetic screening. Identifying new polymorphisms is important for knowing the true mutations in FD.

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

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

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

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

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

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

Pitfalls of X-chromosome inactivation testing in females with Fabry disease

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by mutations in the GLA gene encoding alpha-galactosidase A (AGAL). The impact of X-chromosome inactivation (XCI) on the phenotype of female FD patients remains unclear. In this study we aimed to determine pitfalls of XCI testing in a cohort of 35 female FD patients. XCI was assessed by two methylation-based and two allele-specific expression assays. The results correlated, although some variance among the four assays was observed. GLA transcript analyses identified crossing-over in three patients and detected mRNA instability in three out of four analyzed null alleles. AGAL activity correlated with XCI pattern and was not influenced by the mutation type or by reduced mRNA stability. Therefore, AGAL activity may help to detect crossing-over in patients with unstable GLA alleles. Tissue-specific XCI patterns in six patients, and age-related changes in two patients were observed. To avoid misinterpretation of XCI results in female FD patients we show that (i) a combination of several XCI assays generates more reliable results and minimizes possible biases; (ii) correlating XCI to GLA expression and AGAL activity facilitates identification of cross-over events; (iii) age- and tissue-related XCI specificities of XCI patterning should be considered.

Expert opinion on the recognition, diagnosis and management of children and adults with Fabry disease: a multidisciplinary Turkey perspective

This consensus statement by a panel of Fabry experts aimed to identify areas of consensus on conceptual, clinical and therapeutic aspects of Fabry disease (FD) and to provide guidance to healthcare providers on best practice in the management of pediatric and adult patients with FD. This consensus statement indicated the clinical heterogeneity of FD as well as a large number of pathogenic variants in the GLA gene, emphasizing a need for an individualized approach to patient care. The experts reached consensus on the critical role of a high index of suspicion in symptomatic patients and screening of certain at-risk groups to reveal timely and accurate diagnosis of FD along with an increased awareness of the treating physician about the different kinds of pathogenic variants and their clinical implications. The experts emphasized the crucial role of timely recognition of FD with minimal delay from symptom onset to definite diagnosis in better management of FD patients, given the likelihood of changing the disease's natural history, improving the patients' quality of life and the prognosis after enzyme replacement therapy (ERT) administered through a coordinated, multidisciplinary care approach. In this regard, this consensus document is expected to increase awareness among physicians about unique characteristics of FD to assist clinicians in recognizing FD with a well-established clinical suspicion consistent with pathogenic variants and gender-based heterogeneous clinical manifestations of FD and in translating this information into their clinical practice for best practice in the management of patients with FD.

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.

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.

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

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

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.

Accuracy diagnosis improvement of Fabry disease from dried blood spots: Enzyme activity, lyso-Gb3 accumulation and GLA gene sequencing

The purpose of this study was to examine the applicability of the use of samples in dried blood spot (DBS) for the definitive diagnosis of Fabry disease (FD) in males and females and to compare the diagnostic role of α-galactosidase A activity (α-Gal A), levels of lyso-Gb3 and sequencing of the GLA gene in screening patients with suspected FD. Measurement of α-Gal A activity in suspected FD patients in DBS was made followed by lyso-Gb3 determination and GLA gene sequencing. Of the 2381 subjects analyzed, FD was confirmed in 24 patients. Thirteen different variants were considered like pathogenic, five of which had not been previously described (c.143A > G; c.455A > C; c.487G > T; c.554delA; c.1045_1046insA). None of the patients with normal enzyme activity had FD confirmation. The DBS measurement of α-Gal A was more sensitive than lyso-Gb3 levels in both men and women. Definitive diagnosis of FD from a single DBS is possible, allowing samples to be easily sent from anywhere to the reference laboratory.

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

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

Effects of agalsidase-β administration on vascular function and blood pressure in familial Anderson-Fabry disease

Fabry is an X-linked disorder of glycosphingolipid metabolism that is caused by variants of the GLA gene that codes for α-galactosidase A, leading to lysosomal accumulation of globotriaosylceramide in many cell types. As a result, affected patients manifest with an increased risk of developing ischemic stroke, peripheral neuropathy, cardiac dysfunction, and chronic kidney disease. The protective effects of enzyme replacement therapy (ERT), the milestone in Fabry disease treatment, against globotriaosylceramide (GL-3) accumulation and Fabry disease progression are well known. However, the mechanism of action of ERT is not well understood. Since GL-3 also accumulates in the vascular endothelium, we investigated the effects of agalsidase-β, a recombinant human α-Gal enzyme approved for the treatment of Fabry disease. In this study, vascular function and blood pressure in four adult siblings affected by Fabry disease were evaluated upon agalsidase-β. In all patients, agalsidase-β infusion improves flow-mediated dilation and augmentation index. These changes occurred after the first infusion and were then maintained for the whole period of observation, i.e., 1 year, with more pronounced additional increments in flow-mediated dilation after the second agalsidase-β infusion. Blood pressure was also maintained at optimal levels in all of the patients for the whole period of observation. Our findings show that agalsidase-β administration can improve vascular function in patients suffering from Fabry disease. Changes in flow-mediated dilation and augmentation index persisted for the whole period of observation (1 year), thus suggesting that early substitutive therapy should be promoted in order to protect the cardiovascular system.

Assessing Lysosomal Disorders in the NGS Era: Identification of Novel Rare Variants

Lysosomal storage diseases (LSDs) are a heterogeneous group of genetic disorders with variable degrees of severity and a broad phenotypic spectrum, which may overlap with a number of other conditions. While individually rare, as a group LSDs affect a significant number of patients, placing an important burden on affected individuals and their families but also on national health care systems worldwide. Here, we present our results on the use of an in-house customized next-generation sequencing (NGS) panel of genes related to lysosome function as a first-line molecular test for the diagnosis of LSDs. Ultimately, our goal is to provide a fast and effective tool to screen for virtually all LSDs in a single run, thus contributing to decrease the diagnostic odyssey, accelerating the time to diagnosis. Our study enrolled a group of 23 patients with variable degrees of clinical and/or biochemical suspicion of LSD. Briefly, NGS analysis data workflow, followed by segregation analysis allowed the characterization of approximately 41% of the analyzed patients and the identification of 10 different pathogenic variants, underlying nine LSDs. Importantly, four of those variants were novel, and, when applicable, their effect over protein structure was evaluated through in silico analysis. One of the novel pathogenic variants was identified in the GM2A gene, which is associated with an ultra-rare (or misdiagnosed) LSD, the AB variant of GM2 Gangliosidosis. Overall, this case series highlights not only the major advantages of NGS-based diagnostic approaches but also, to some extent, its limitations ultimately promoting a reflection on the role of targeted panels as a primary tool for the prompt characterization of LSD patients.

Analysis of the alpha galactosidase gene: mutation profile and description of two novel mutations with extensive literature review in Turkish population

Objectives Fabry disease (FD, OMIM #301500) is a rare and progressive X-linked lysosomal storage disorder. FD is caused by mutations in the GLA gene on chromosome Xq22. Methods In this article, we aimed to present the largest sample of GLA mutation spectrum including common and novel variants in Turkish population. GLA gene sequence analysis was performed on the subjects who applied to the department of medical genetics with the preliminary diagnosis of FD between 2013 and 2018. Results We detected 22 different mutations as two novel [(p.F69S(c.206T>C), p.P205A (c.613C>G)] and 20 previously reported GLA mutations in 47 individuals from 22 unrelated families. These mutations included 14 missense mutations, four nonsense mutations, two small deletions, one small deletion/insertion and one small insertion. Major clinical findings of the female case with p.F69S(c.206T>C) mutation were cornea verticillata, acroparesthesia, angiokeratoma, psychiatric and gastrointestinal symptoms. Other novel mutation (p.P205A [c.613C>G]) was carried by a male case presenting gastrointestinal symptoms. Conclusions We described clinical findings of two cases that had novel mutations to provide more insight in genotype-phenotype correlation. We presented the largest mutation spectrum in Turkish population and reviewed previous mutations in this article.

A comprehensive testing algorithm for the diagnosis of Fabry disease in males and females

PURPOSE

Successful diagnosis of Fabry disease is often delayed or missed in patients, especially females, due to clinical heterogeneity and a lack of disease awareness. We present our experience testing for Fabry disease in high risk populations and discuss the relative sensitivities of α-galactosidase A (α-Gal A) enzyme activity in blood, plasma lyso-globotriaosylceramide (lyso-Gb₃) biomarker, and GLA gene sequencing as diagnostic tests for Fabry disease in both males and females.

METHODS

Patients with a clinical suspicion of Fabry disease were evaluated with enzyme analysis, biomarker analysis, and GLA sequencing. All three assays were performed from a single tube of EDTA blood. α-Gal A activity was determined in dried blood spots using a fluorometric assay, plasma lyso-Gb₃ by UPLC-MS/MS, and GLA analysis by Sanger sequencing.

RESULTS

Peripheral blood samples were received from 94 males and 200 females, of which 29% of males and 22% of females had a positive family history of Fabry disease. A likely pathogenic or pathogenic variant was identified in 87 (30%) patients (50 males, 37 females), confirming a diagnosis of Fabry disease. Of the remaining patients, 178 (61%) were determined to be unaffected based on normal enzyme activity (males) or normal lyso-Gb₃ and negative sequencing results (females). A VUS was identified in 29 (10%) patients. The positive and negative predictive value of plasma lyso-Gb₃ was 100% and 97% in males and 100% and 99% in females, respectively. This compares with 84% and 100% in males, and 58% and 50% in females for α-Gal A activity testing, respectively.

CONCLUSIONS

Plasma lyso-Gb₃ has high sensitivity and specificity for Fabry disease in males and females, and provides supportive diagnostic information when gene sequencing results are negative or inconclusive. α-Gal A activity in dried blood spots (DBS) has high sensitivity, but lower specificity for Fabry disease in males, as not all males with low α-Gal A activities were confirmed to have Fabry disease. Therefore, reflexing to gene sequencing and plasma lyso-Gb₃ is useful for disease confirmation in males. For females, we found that first tier testing consisting of GLA sequencing and plasma lyso-Gb₃ analysis provided the greatest sensitivity and specificity. Enzyme testing has lower sensitivity in females and is therefore less useful as a first-tier test. Enzyme analysis in females may still be helpful as a second-tier test in cases where molecular testing and plasma lyso-Gb₃ analysis are uninformative and in vitro enzyme activity is low.

SUMMARY

Sex-specific testing algorithms that prioritize tests with high specificity and sensitivity offer an effective means of identifying individuals with Fabry disease.

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

BACKGROUND

Fabry disease (α-galactosidase deficiency) is an X-linked genetic disease caused by a variety of pathogenic GLA variants. The phenotypic heterogeneity is considerable, with two major forms, classic and later-onset disease, but adjudication of clinical phenotype is currently lacking for many variants. We aimed to determine consensus phenotypic classification for previously unclassified GLA variants from the GLA-specific fabry-database.org database.

METHODS

A Fabry disease genotype-phenotype workgroup developed a five-stage iterative system based on expert clinical assessment, published literature and clinical evidence of pathogenicity using a 2-point scoring system based on clinical hallmarks of classic disease. Kaplan-Meier (KM) analysis of severe clinical event-free survival was used as final validation. Results were compared with those from web-based disease databases and in silico pathogenicity prediction programmes.

RESULTS

Final consensus on classifications of 'pathogenic' was achieved for 32 of 33 GLA variants (26 'classic' phenotype, 171 males; 6 'later-onset' phenotype, 57 males). One variant remained of uncertain significance. KM curves were similar for the known fabry-database.org database phenotypes and when workgroup consensus classifications were added, and the curves retained the same separation between 'classic' and 'later-onset' phenotypes.

CONCLUSION

The iterative system implemented by a Fabry disease genotype-phenotype workgroup achieved phenotypic classifications for variants that were previously unclassified. Clinical pathogenicity associated with a particular GLA variant defined in affected males appears to have predictive value and also generally correlates with risk for affected females. The newly established classifications can be of benefit to the clinical care of Fabry patients harbouring these variants.

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.

Functional evaluation of a novel GLA causative mutation in Fabry disease

Background

Fabry disease (FD), a rare X‐linked α‐galactosidase A (GLA) deficiency, resulting in progressive lysosomal accumulation of globotriaosylceramide in a variety of cell types. More and more disease‐causing mutations in GLA have been identified in FD due to the advancement of molecular diagnostic tools. We found a novel mutation in a Chinese family with predominant Fabry's disease nephropathy.

Methods

All coding regions and exon–intron splice junctions of the GLA gene were sequenced to find sequence variations. We evaluated the impact on the GLA protein by analysis of the GLA mRNA, by sequential analysis and homology modeling, and by site‐directed mutagenesis and in vitro expression studies.

Results

We identified a novel heterozygous missense mutation c.280T>C in our patient with variable phenotypic presentations of renal involvement. The novel GLA variant results in low expression of GLA mRNAs, impaired or loss of the disulfate bridge structure of wild‐type GLA, reduced GLA activity and defected nuclear shape in the GFP‐GLA‐MT transfected HEK293T cells.

Conclusion

A novel GLA missense mutation, c.280T>C (Cys94Arg), was found in a Chinese family with predominant renal manifestations of FD. Our study reveals the pathogenesis of c.280T>C mutation to FD and provides scientific foundation for accurate diagnosis and precise medical intervention for FD.

Elevated Inflammatory Plasma Biomarkers in Patients With Fabry Disease: A Critical Link to Heart Failure With Preserved Ejection Fraction

Background Because systemic inflammation and endothelial dysfunction lead to heart failure with preserved ejection fraction, we characterized plasma levels of inflammatory and cardiac remodeling biomarkers in patients with Fabry disease ( FD ). Methods and Results Plasma biomarkers were studied in multicenter cohorts of patients with FD (n=68) and healthy controls (n=40). Plasma levels of the following markers of inflammation and cardiac remodeling were determined: tumor necrosis factor ( TNF ), TNF receptor 1 ( TNFR 1) and 2 ( TNFR 2), interleukin-6, matrix metalloprotease-2 ( MMP -2), MMP -8, MMP -9, galectin-1, galectin-3, B-type natriuretic peptide ( BNP ), midregional pro-atrial natriuretic peptide ( MR -pro ANP ), and globotriaosylsphingosine. Clinical profile, cardiac magnetic resonance imaging, and echocardiogram were reviewed and correlated with biomarkers. Patients with FD had elevated plasma levels of BNP , MR -pro ANP , MMP -2, MMP -9, TNF , TNFR 1, TNFR 2, interleukin-6, galectin-1, globotriaosylsphingosine, and analogues. Plasma TNFR 2, TNF , interleukin-6, MMP -2, and globotriaosylsphingosine were elevated in FD patients with left ventricular hypertrophy, whereas diastolic dysfunction correlated with higher BNP , MR -pro ANP , and MMP -2 levels. Patients with late gadolinium enhancement on cardiac magnetic resonance imaging had greater levels of BNP , MR -pro ANP , TNFR 1, TNFR 2, and MMP -2. Plasma BNP , MR -pro ANP , MMP -2, MMP -8, TNF , TNFR 1, TNFR 2, galectin-1, and galectin-3 were elevated in patients with renal dysfunction. Patients undergoing enzyme replacement therapy who have more severe disease had higher MMP -2, TNF , TNFR 1, TNFR 2, and globotriaosylsphingosine analogue levels. Conclusions Inflammatory and cardiac remodeling biomarkers are elevated in FD patients and correlate with disease progression. These features are consistent with a phenotype dominated by heart failure with preserved ejection fraction and suggest a key pathogenic role of systemic inflammation in FD .

Clinical impact of the alpha-galactosidase A gene single nucleotide polymorphism -10C>T: A single-center observational study

Single nucleotide polymorphisms (SNPs) in the alpha-galactosidase A gene region (GLA) have been discussed as potential cause of symptoms and organ manifestations similarly to those seen in Fabry disease (FD). However, due to scarce data, clinical implications remain limited. The aim of the present study was to investigate the clinical impact of -10C>T SNP in the GLA.Prospective single-center observational study to determine the natural history and outcome of FD.Subjects initially referred to the Fabry Center for Interdisciplinary Therapy Würzburg (FAZIT) for management of suspected FD (11 women, 2 men, mean age 42 ± 10 years) who were tested negative for coding GLA mutations but positive for the noncoding -10C>T SNP underwent comprehensive characterization for therapy recommendation.All subjects reported at least 1 neurological, but no cardiac or renal symptoms. In 7 patients, pain of unknown etiology was reported and 3 patients had a history of cryptogenic stroke. In all patients, α-GAL activity was at a lower limit, ranging between 0.27 and 0.45 nmol/min per mg protein (reference: 0.4-1.0), while plasma Lyso-Gb3 levels remained normal (range 0.39 ± 0.33; reference: ≤0.9 ng/mL). For both hemizygous subjects investigated, brain magnetic resonance imaging revealed unspecific white matter lesions. One of these subjects had suffered from severe early-onset stroke, the other showed mild hypertrophic cardiomyopathy.Presence of isolated heterozygous -10C >T SNP is not associated with clinically relevant symptoms or organ manifestations as seen in FD. Respective polymorphisms might, however, play a role in modifying disease severity in FD. Great care has to be taken in respective subjects suspected to suffer from nonclassical FD in order to prevent unnecessary Fabry-specific therapy.

Fabry disease in the Spanish population: observational study with detection of 77 patients

Background

Fabry disease is a multisystemic lysosomal storage disorder caused by the impairment of α-galactosidase A. The incidence of this rare disease is underestimated due to delayed diagnosis. Moreover, the management of the identified subjects is often complicated by the detection of variants of unclear diagnostic interpretation, usually identified in screening studies. We performed an observational study based on biochemical and genetic analysis of 805 dried blood spot samples from patients with clinical symptoms or family history of this pathology, which were collected from 109 Spanish hospitals, all over the country.

Results

We identified 77 new diagnosed patients with mutations related to classical Fabry disease, as well as 2 subjects with c.374A > T; p.His125Leu, a possible new mutation that need to be confirmed. Additionally, we detected 8 subjects carrying genetic variants possibly linked to late onset Fabry disease (p.Arg118Cys and p.Ala143Thr), 4 cases with polymorphism p.Asp313Tyr and 36 individuals with single nucleotide polymorphisms in intronic regions of GLA. Five of the identified mutations (c.431delG; c.1182delA; c.374A > T; c.932 T > C; c.125 T > A; c.778G > A), which were associated with a classical phenotype have not been previously described. Moreover 3 subjects presenting complex haplotypes made up by the association of intronic variants presented impaired levels of GLA transcripts and Gb3 deposits in skin biopsy.

Conclusions

Enzymatic screening for Fabry Disease in risk population (2 or more clinical manifestations or family history of the disease) helped to identify undiagnosed patients and unravel the impairment of GLA expression in some subjects with complex haplotypes.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0792-8) contains supplementary material, which is available to authorized users.

Phenotype and biochemical heterogeneity in late onset Fabry disease defined by N215S mutation

BACKGROUND

Fabry disease (FD) results from X-linked inheritance of a mutation in the GLA gene, encoding for alpha galactosidase A, and is characterized by heterogeneous clinical manifestations. Two phenotypes have been described "Classic" and "late onset" which cannot be predicted exclusively by genotype. The latter has been considered an attenuated form of the disease often affecting a single organ system commonly the heart. Recent studies have demonstrated that cardiac outcomes are similar in patients with classic and late onset mutations. In this study we investigate the relationship between clinical heterogeneity and plasma lyso-Gb3 in a large single centre cohort of N215S patients and compare this to patients with other mutations.

METHODS

In this single-centre, retrospective, cross-sectional study we analysed a cohort of 251 FD patients: 84 N215S mutation (37 males) and 167 non-N215S mutations (58 males). The Mainz severity score index (MSSI) was used as an index of overall disease severity. Cardiac function and morphology were assessed by electrocardiogram and echocardiogram. Left ventricular mass was calculated using the Devereux formula and the left ventricular mass index (LVMI) calculated to adjust for height (g/m2.7). The presence of white matter lesions was assessed by cerebral MRI or computed tomography (CT). GFR was measured by radio-isotope (chromium-EDTA) method and adjusted for patient height (ml/min/m2.7), and urinary protein quantification was undertaken by 24 hour urine collection. Plasma globotriaosylsphingosine (lyso-Gb3) was analysed prior to ERT in 84 patients.

RESULTS

N215S patients showed later symptom onset (males: p< 0.0001, females: p<0.03), later development of left ventricular hypertrophy (LVH) (median survival without LVH: 41 (non-N215S) vs. 64 (N215S) years, p< 0.0001), later development of proteinuria (median survival without proteinuria 43 (non-N215S) vs 71 years (N215S), p< 0.0001), later occurrence of cerebrovascular events (stroke/ Transient Ischaemic Attacks (TIA); median survival without stroke: 74 years (non-N215S) vs. not reached (N215S), p< 0.02), later decline in renal function to GFR <60 ml/min/1.73m2 (median survival: 56 (non-N215S) vs. 72 (N215S) years, p< 0.01), and greater overall survival (median survival 81 (N215S) vs. 66 (non-N215S) years, p< 0.0006). Lyso-Gb3 was found to be less elevated in N215S compared to non-N215S male and female patients. However, the N215S population eventually reached an overall severity measured by MSSI comparable to the non-N215S without equivalent elevation of lyso-Gb3 (means: 6.7 vs. 74.3 nmol/L, p < 0.001). In addition, N215S patients showed strong correlations between lyso-Gb3 levels and LVMI, GFR, and MSSI. These associations became stronger when we investigated individuals' life time exposure to lyso-Gb3 (calculated as [lyso-Gb3]*age): MSSI (r2 = 0.88, p< 0.0001), LVMI (r2 = 0.59, p< 0.005), and GFR (r2 = 0.75, p = 0.0001).

CONCLUSION

These results demonstrate that the N215S mutation results in a late onset phenotype involving the heart and other organs. Correlations between clinical manifestations and plasma lyso-Gb3 variations in this group suggest a Fabry-relevant disease mechanism for the heterogeneity observed in this group.

Female Fabry disease patients and X-chromosome inactivation

Fabry disease is an X-linked inherited lysosomal storage disorder caused by mutations in the gene encoding α-galactosidase A (GLA). Once it was thought to affect only hemizygous males. Over the last fifteen years, research has shown that most females carrying mutated allele also develop symptoms, demonstrating a wide range of disease severity, from a virtually asymptomatic to more classical profile, with cardiac, renal, and cerebrovascular manifestations. This variable expression in females is thought to be influenced by the process of X-chromosome inactivation (XCI). The aim of this study was to assess severity of the clinical phenotype, to analyze XCI patterns, and to estimate their effect on disease manifestation in twelve female Fabry disease patients from five unrelated Polish families. Our analyses revealed that patients presented with the broad range of disease expression - from mild to severe, and their clinical involvement did not correlate with XCI profiles. Female carriers of the mutation in the GLA gene with the random XCI may present with the wide range of disease signs and symptoms. Thus, XCI is not a main factor in the phenotype variability of Fabry disease manifestation in heterozygous females.

A simple method for quantification of plasma globotriaosylsphingosine: Utility for Fabry disease

Fabry disease (FD) results from impaired globotriaosylceramide (Gb3) catabolism, due to a deficiency of the lysosomal hydrolase, α-galactosidase A (α-GalA). As a direct consequence, the deacetylated derivative, globotriaosylsphingosine (lyso-Gb3), is produced and contemporary evidence exemplifies its use as a biomarker. Here we developed a simple method to enable quantification of lyso-Gb3 in just 0.01mL of plasma and explored its concentration in a cohort of 73 Australian FD patients, as well as in individuals with other sphingolipidoses. In 2000 patients without FD, but with related metabolic conditions, lyso-Gb3 returned concentrations of <5pmol/mL. In the FD cohort, 53/60 patients with classical mutations returned lyso-Gb3 concentrations≥5pmol/mL whereas only 4/13 patients with "late-onset" mutations had lyso-Gb3≥5pmol/mL. Five females with normal α-GalA activity and genetically confirmed FD returned lyso-Gb3≥5pmol/mL. The prevalence of clinically significant disease including cardiomyopathy, nephropathy and cerebrovascular disease was congruent with higher lyso-Gb3 concentrations. Repeat testing was available for 51 patients-26 undergoing enzyme replacement therapy-and concentrations of lyso-Gb3 remained unaltered throughout 6-18 months independent of sex, mutation or treatment status. Our data suggest that the optimum use of lyso-Gb3 resides in laboratory confirmation of classical FD and for monitoring at least the initial response to therapeutic intervention. There is no evidence that lyso-Gb3 can inform on clinical events.

Clinical characteristics and mutation spectrum of GLA in Korean patients with Fabry disease by a nationwide survey: Underdiagnosis of late-onset phenotype

Fabry disease is a rare X-linked lysosomal storage disorder caused by an α-galactosidase A deficiency. The progressive accumulation of globotriaosylceramide (GL-3) results in life-threatening complications, including renal, cardiac, and cerebrovascular diseases. This study investigated the phenotypic and molecular spectra of GLA mutations in Korean patients with Fabry disease using a nationwide survey.This study included 94 patients from 46 independent pedigrees: 38 adult males, 46 symptomatic females, and 10 pediatric males. Each diagnosis was based on an enzyme assay and GLA gene mutation analysis.The mean age at presentation was 24 years (range, 5-65 years); however, the diagnoses were delayed by 21 ± 19 years after the onset of symptoms. Those patients with late-onset Fabry disease were diagnosed by family screening or milder symptoms at a later age. Forty different mutations were identified: 20 missense (50%), 10 nonsense (25%), 8 frameshift (20%), and 2 splice site (5%) mutations. Five of them were novel. IVS4+919G>A (c.936+919 G>A) was not detected among the 6505 alleles via newborn screening using dried blood spots. Enzyme replacement therapy (ERT) was performed in all the males and pediatric patients, whereas 75% of the symptomatic females underwent ERT for 4.2 ± 3.6 years.This study described the demographic data, wide clinical spectrum of phenotypes, and GLA mutation spectrum of Fabry disease in Korea. Most of the patients had classical Fabry disease, with a 4 times higher incidence than that of late-onset Fabry disease, indicating an underdiagnosis of mild, late-onset Fabry disease.

Risk factors for severe clinical events in male and female patients with Fabry disease treated with agalsidase beta enzyme replacement therapy: Data from the Fabry Registry

BACKGROUND

Fabry disease, an X-linked lysosomal storage disorder, causes intracellular accumulation of glycosphingolipids leading to progressive renal, cardiovascular, and cerebrovascular disease, and premature death.

METHODS

This longitudinal Fabry Registry study analyzed data from patients with Fabry disease to determine the incidence and type of severe clinical events following initiation of enzyme replacement therapy (ERT) with agalsidase beta, as well as risk factors associated with occurrence of these events. Severe events assessed included chronic dialysis, renal transplantation, cardiac events, stroke, and death.

RESULTS

The analyses included 969 male and 442 female Fabry patients. The mean age at first agalsidase beta infusion was 35 and 44, and median treatment follow-up 4.3years and 3.2years, respectively. Among males, cardiac events were the most common on-ERT events, followed by renal, stroke, and non-cardiac death. Among females, cardiac events were also most common followed by stroke and renal events. Patients with on-ERT events had significantly more advanced cardiac and renal disease at baseline as compared with patients without on-ERT events. Severe events were also associated with older age at ERT initiation (males and females), a history of pre-ERT events (females; approaching statistical significance in males), and a higher urinary protein/creatinine ratio (females). Approximately 65% of patients with pre-ERT events did not experience subsequent on-ERT events. Of patients without pre-ERT events, most (84% of males, 92% of females) remained event-free.

CONCLUSIONS

Patients with on-ERT severe events had more advanced Fabry organ involvement at baseline than those without such events and patients who initiated ERT at a younger age had less residual risk of on-ERT events. The observed patterns of residual risk may aid clinicians in multidisciplinary monitoring of male and female patients with Fabry disease receiving ERT, and in determining the need for administration of adjunctive therapies.

Genotype: A Crucial but Not Unique Factor Affecting the Clinical Phenotypes in Fabry Disease

Numerous α-galactosidase A (α-gal A) gene (GLA) mutations have been identified in Fabry disease (FD), but studies on genotype-phenotype correlation are limited. This study evaluated the features of GLA gene mutations and genotype-phenotype relationship in Chinese FD patients. Gene sequencing results, demographic information, clinical history, and laboratory findings were collected from 73 Chinese FD patients. Totally 47 mutations were identified, including 23 novel mutations which might be pathogenic. For male patients, those with frameshift and nonsense mutations presented the classical FD, whereas those with missense mutations presented both of classical and atypical phenotypes. Interestingly, two male patients with missense mutation p.R356G from two unrelated families, and two with p.R301Q from one family presented different phenotypes. A statistically significant association was found between the levels of α-gal A enzyme activity and ocular changes in males, though no significant association was found between residual enzyme activity level and genotype or clinical phenotypes. For female patients, six out of seven with frameshift mutations and one out of nine with missense mutation presented the classical FD, and α-gal A activity in those patients was found to be significantly lower than that of patients with atypical phenotypes (13.73 vs. 46.32 nmol/ml/h/mg). Our findings suggest that the α-gal A activity might be associated with the clinical severity in female patients with FD. But no obvious associations between activity level of α-gal A and genotype or clinical phenotypes were found for male patients.

Fabry's disease: an example of cardiorenal syndrome type 5

Cardiorenal syndrome type 5 (CRS-5) includes conditions where there is a simultaneous involvement of the heart and kidney from a systemic disorder. This is a bilateral organ cross talk. Fabry's disease (FD) is a devastating progressive inborn error of metabolism with lysosomal glycosphingolipid deposition in variety of cell types, capillary endothelial cells, renal, cardiac and nerve cells. Basic effect is absent or deficient activity of lysosomal exoglycohydrolase a-galactosidase A. Renal involvement consists of proteinuria, isosthenuria, altered tubular function, presenting in second or third decade leading to azotemia and end-stage renal disease in third to fifth decade mainly due to irreversible changes to glomerular, tubular and vascular structures, especially highlighted by podocytes foot process effacement. Cardiac involvement consists of left ventricular hypertrophy, right ventricular hypertrophy, arrhythmias (sinus node and conduction system impairment), diastolic dysfunction, myocardial ischemia, infarction, transmural replacement fibrosis, congestive heart failure and cardiac death. Management of FD is based on enzymatic replacement therapy and control of renal (with anti-proteinuric agents such as angiotensin-converting enzyme inhibitors-and/or angiotensin II receptor blockers), brain (coated aspirin, clopidogrel and statin to prevent strokes) and heart complications (calcium channel blockers for ischemic cardiomyopathy, warfarin and amiodarone or cardioverter device for arrhythmias).

Target-enrichment sequencing and copy number evaluation in inherited polyneuropathy

OBJECTIVE

To assess the efficiency of target-enrichment next-generation sequencing (NGS) with copy number assessment in inherited neuropathy diagnosis.

METHODS

A 197 polyneuropathy gene panel was designed to assess for mutations in 93 patients with inherited or idiopathic neuropathy without known genetic cause. We applied our novel copy number variation algorithm on NGS data, and validated the identified copy number mutations using CytoScan (Affymetrix). Cost and efficacy of this targeted NGS approach was compared to earlier evaluations.

RESULTS

Average coverage depth was ∼760× (median = 600, 99.4% > 100×). Among 93 patients, 18 mutations were identified in 17 cases (18%), including 3 copy number mutations: 2 PMP22 duplications and 1 MPZ duplication. The 2 patients with PMP22 duplication presented with bulbar and respiratory involvement and had absent extremity nerve conductions, leading to axonal diagnosis. Average onset age of these 17 patients was 25 years (2-61 years), vs 45 years for those without genetic discovery. Among those with onset age less than 40 years, the diagnostic yield of targeted NGS approach is high (27%) and cost savings is significant (∼20%). However, the cost savings for patients with late onset age and without family history is not demonstrated.

CONCLUSIONS

Incorporating copy number analysis in target-enrichment NGS approach improved the efficiency of mutation discovery for chronic, inherited, progressive length-dependent polyneuropathy diagnosis. The new technology is facilitating a simplified genetic diagnostic algorithm utilizing targeted NGS, clinical phenotypes, age at onset, and family history to improve diagnosis efficiency. Our findings prompt a need for updating the current practice parameters and payer guidelines.

Embolic Strokes of Unknown Source and Cryptogenic Stroke: Implications in Clinical Practice

Up to a third of strokes are rendered cryptogenic or of undetermined etiology. This number is specifically higher in younger patients. At times, inadequate diagnostic workups, multiple causes, or an under-recognized etiology contributes to this statistic. Embolic stroke of undetermined source, a new clinical entity particularly refers to patients with embolic stroke for whom the etiology of embolism remains unidentified despite through investigations ruling out established cardiac and vascular sources. In this article, we review current classification and discuss important clinical considerations in these patients; highlighting cardiac arrhythmias and structural abnormalities, patent foramen ovale, paradoxical sources, and potentially under-recognized, vascular, inflammatory, autoimmune, and hematologic sources in relation to clinical practice.

Time to treatment benefit for adult patients with Fabry disease receiving agalsidase β: data from the Fabry Registry

Background

Agalsidase β is a form of enzyme replacement therapy for Fabry disease, a genetic disorder characterised by low α-galactosidase A activity, accumulation of glycosphingolipids and life-threatening cardiovascular, renal and cerebrovascular events. In clinical trials, agalsidase β cleared glycolipid deposits from endothelial cells within 6 months; clearance from other cell types required sustained treatment. We hypothesised that there might be a ‘lag time’ to clinical benefit after initiating agalsidase β treatment, and analysed the incidence of severe clinical events over time in patients receiving agalsidase β.

Methods

The incidence of severe clinical events (renal failure, cardiac events, stroke, death) was studied in 1044 adult patients (641 men, 403 women) enrolled in the Fabry Registry who received agalsidase β (average dose 1 mg/kg every 2 weeks) for up to 5 years.

Results

The incidence of all severe clinical events was 111 per 1000 person-years (95% CI 84 to 145) during the first 6 months. After 6 months, the incidence decreased and remained stable within the range of 40–58 events per 1000 patient-years. The largest decrease in incidence rates was among male patients and those aged ≥40 years when agalsidase β was initiated.

Conclusions

Contrary to the expected increased incidence of severe clinical events with time, adult patients with Fabry disease had decreased incidence of severe clinical events after 6 months treatment with agalsidase β 1 mg/kg every 2 weeks.

Trial registration number

NCT00196742.

Functional and Clinical Consequences of Novel α-Galactosidase A Mutations in Fabry Disease

Fabry disease (FD) is a rare metabolic disorder of glycosphingolipid storage caused by mutations in the GLA gene encoding lysosomal hydrolase α-galactosidase A (α-gal A). Recently, the diagnostic procedure for FD has advanced in several ways, through the development of a specific biomarker (lyso-Gb3) and the implementation of newborn screenings, which acted as a catalyst to augment general awareness of the disease. Heterologous over-expression of α-gal A variants and subsequent in vitro measurement of enzyme activity provided molecular data to elucidate the relationship between mutation, enzyme damage, lyso-Gb3 biomarker levels, and clinical phenotype. This knowledge is the foundation for improved counseling with regard to prognosis and therapeutic decisions. Herein, we resume the approach of in vitro characterization, with a further 73 mainly novel GLA gene mutations. Patient lyso-Gb3 data were available for most of the mutations. All mutations were tested for responsiveness to pharmacological chaperone treatment and phenotypic data for 61 hemizygous male and 116 heterozygous female patients carrying a mutation associated with ≥ 20% residual activity, formerly classified as "mild" variant, were collected in order to evaluate the pathogenicity. We conclude that a mild GLA variant is typically characterized by high residual enzyme activity and normal biomarker levels. We found evidence that these variants can still be classified as a distinctive, but milder, sub-type of FD.

Reduction of Plasma Globotriaosylsphingosine Levels After Switching from Agalsidase Alfa to Agalsidase Beta as Enzyme Replacement Therapy for Fabry Disease

INTRODUCTION

Agalsidase alfa and agalsidase beta, recombinant enzyme preparations for treatment of Fabry disease (FD), have different approved dosing schedules: 0.2 mg/kg and 1.0 mg/kg every other week (EOW), respectively.

METHODS

This open-label, multicenter, exploratory phase 4 study evaluated plasma globotriaosylsphingosine (lyso-GL-3) and plasma and urine globotriaosylceramide (GL-3) levels at baseline and 2, 4, and 6 months after the switch from agalsidase alfa (0.2 mg/kg EOW for ≥12 months) to agalsidase beta (1.0 mg/kg EOW) in 15 male patients with FD. Immunoglobulin (Ig)G antidrug antibody titers were assessed, and safety was monitored throughout the study.

RESULTS

Plasma lyso-GL-3 concentrations decreased significantly within 2 months after switch and reductions continued through month 6 (mean absolute changes, -12.8, -16.1, and -16.7 ng/mL at 2, 4, and 6 months, respectively; all P < 0.001). The mean percentage reduction from baseline was 39.5% (P < 0.001) at month 6. For plasma GL-3, the mean absolute change from baseline (-0.9 μg/mL) and percentage reduction (17.9%) at month 6 were both significant (P < 0.05). Urine GL-3 measurements showed intra-patient variability and changes from baseline were not significant. No clinical outcomes were assessed in this 6-month study, and, therefore, no conclusions can be drawn regarding the correlation of observed reductions in glycosphingolipid concentrations with clinically relevant outcomes. There were no differences in IgG antidrug antibody titers between the two enzymes. The switch from agalsidase alfa to agalsidase beta was well tolerated.

CONCLUSION

Plasma lyso-GL-3 and GL-3 levels reduced after switching from agalsidase alfa to agalsidase beta, indicating that agalsidase beta has a greater pharmacodynamic effect on these markers at the recommended dose. These data further support the use of agalsidase beta 1.0 mg/kg EOW as enzyme replacement therapy in FD.

Clinical and genetic predictors of major cardiac events in patients with Anderson-Fabry Disease

BACKGROUND

Anderson-Fabry Disease (AFD) is an X linked lysosomal storage disorder caused by mutations in the α-galactosidase A gene. Some mutations are associated with prominent and, in many cases, exclusive cardiac involvement. The primary aims of this study were to determine the incidence of major cardiac events in AFD and to identify clinical and genetic predictors of adverse outcomes.

METHODS AND RESULTS

We studied 207 patients with AFD (47% male, mean age 44 years, mean follow-up 7.1 years). Fifty-eight (28%) individuals carried mutations that have been previously associated with a cardiac predominant phenotype. Twenty-one (10%) developed severe heart failure (New York Heart Association functional class (NYHA) ≥3), 13 (6%) developed atrial fibrillation (AF), 13 (6%) received devices for the treatment of bradycardia; there were a total of 7 (3%) cardiac deaths. The incidence of the primary endpoint (a composite of new onset AF, NYHA ≥ 3 symptoms, device insertion for bradycardia and cardiac death) was 2.64 per 100 person-years (CI 1.78 to 3.77). Age (HR 1.04, CI 1.01 to 1.08, p=0.004), Mainz Severity Score Index score (HR 1.05, CI 1.01 to 1.09, p=0.012) and QRS duration (HR 1.03, CI 1.00 to 1.05, p=0.020) were significant independent predictors of the primary endpoint. The presence of a cardiac genetic variant did not predict the primary end point.

CONCLUSIONS

AFD is associated with a high burden of cardiac morbidity and mortality. Adverse cardiac outcomes are associated with age, global disease severity and advanced cardiac disease but not the presence of cardiac genetic variants.

The alpha-galactosidase A p.Arg118Cys variant does not cause a Fabry disease phenotype: data from individual patients and family studies

Lysosomal α-galactosidase A (α-Gal) is the enzyme deficient in Fabry disease (FD), an X-linked glycosphingolipidosis caused by pathogenic mutations affecting the GLA gene. The early-onset, multi-systemic FD classical phenotype is associated with absent or severe enzyme deficiency, as measured by in vitro assays, but patients with higher levels of residual α-Gal activity may have later-onset, more organ-restricted clinical presentations. A change in the codon 118 of the wild-type α-Gal sequence, replacing basic arginine by a potentially sulfhydryl-binding cysteine residue - GLA p.(Arg118Cys) -, has been recurrently described in large FD screening studies of high-risk patients. Although the Cys118 allele is associated with high residual α-Gal activity in vitro, it has been classified as a pathogenic mutation, mainly on the basis of theoretical arguments about the chemistry of the cysteine residue. However its pathogenicity has never been convincingly demonstrated by pathology criteria. We reviewed the clinical, biochemical and histopathology data obtained from 22 individuals of Portuguese and Spanish ancestry carrying the Cys118 allele, including 3 homozygous females. Cases were identified either on the differential diagnosis of possible FD manifestations and on case-finding studies (n=11; 4 males), or on unbiased cascade screening of probands' close relatives (n=11; 3 males). Overall, those data strongly suggest that the GLA p.(Arg118Cys) variant does not segregate with FD clinical phenotypes in a Mendelian fashion, but might be a modulator of the multifactorial risk of cerebrovascular disease. The Cys118 allelic frequency in healthy Portuguese adults (n=696) has been estimated as 0.001, therefore not qualifying for "rare" condition.