The mutation D313Y may be associated with nervous system manifestations in Fabry disease

In vitro characterization of cells derived from a patient with the GLA variant c.376A>G (p.S126G) highlights a non-pathogenic role in Fabry disease

Fabry disease (FD) is a life-limiting disorder characterized by intracellular globotriaosylceramide (Gb3) accumulations. The underlying α-galactosidase A (α-GAL A) deficiency is caused by variants in the gene GLA. Variants of unknown significance (VUS) are frequently found in GLA and challenge clinical management. Here, we investigated a 49-year old man with cryptogenic lacunar cerebral stroke and the chance finding of the VUS S126G, who was sent to our center for diagnosis and initiation of a costly and life-long FD-specific treatment. We combined clinical examination with in vitro investigations of dermal fibroblasts (HDF), induced pluripotent stem cells (iPSC), and iPSC-derived sensory neurons. We analyzed α-GAL A activity in iPSC, Gb3 accumulation in all three cell types, and action potential firing in sensory neurons. Neurological examination and small nerve fiber assessment was normal except for reduced distal skin innervation. S126G iPSC showed normal α-GAL A activity compared to controls and no Gb3 deposits were found in all three cell types. Baseline electrophysiological characteristics of S126G neurons showed no difference compared to healthy controls as investigated by patch-clamp recordings. We pioneer multi-level cellular characterization of the VUS S126G using three cell types derived from a patient and provide further evidence for the benign nature of S126G in GLA, which is of great importance in the management of such cases in clinical practice.

Fabry disease due to D313Y variant with renal failure and possible cardiac involvement: a case report

Background

This is a case report of a patient with Anderson-Fabry disease (AFD) due to the D313Y variant on the a-galactosidase A (GLA) gene on migalastat treatment and severe chronic kidney disease referred to our unit to assess possible cardiac involvement.

Case summary

A 53-year-old man with chronic kidney disease due to AFD and a medical history of revascularized coronary artery disease, chronic atrial fibrillation, and arterial hypertension was referred to our unit for evaluation of possible cardiac involvement in the context of AFD. Biochemical evaluation reported reduced serum alpha-galactosidase A activity and borderline abnormal serum lyso-Gb₃ enzyme activity. The patient had also history of acroparesthesias, dermatological presentation of multiple angiokeratomas, severe kidney impairment with an estimated glomerular filtration rate (eGFR) of 30 mL/min/1.73m² by the age of 16, and microalbuminuria that cumulatively set the diagnosis of AFD. Transthoracic echocardiogram showed left ventricular concentric hypertrophy with left ventricular ejection fraction of 45%. Cardiac magnetic resonance showed findings in keeping with ischaemic heart disease (IHD), i.e. akinesia and subendocardial scarring of the basal anterior and the entirety of the septum and the true apex; in addition, there was severe asymmetrical hypertrophy of the basal anteroseptum (max 18 mm), evidence of low-grade myocardial inflammation, and mid-wall fibrosis of the basal inferior and inferolateral wall, suggesting a cardiomyopathic process-myocardial disease which could not be explained solely by IHD or well-controlled hypertension.

Discussion

This is the first case of possible cardiac involvement in a patient with AFD due to the D313Y variant. This case demonstrates the diagnostic challenges of cardiac involvement in AFD, especially in the presence of a concomitant underlying pathology.

How relevant are cerebral white matter lesions in the D313Y variant of the α-galactosidase A gene? Neurological, cardiological, laboratory, and MRI data of 21 patients within a follow-up of 3 years

BACKGROUND

Fabry disease is an inherited metabolic disorder with various symptoms. Neurological manifestations are small fiber neuropathy, cerebral white matter lesions (WML), megadolicho basilar artery, and stroke. The relevance of the D313Y variant in the galactosidase alpha gene is controversially discussed.

OBJECTIVES

We aimed at elucidating the implications of this differential diagnosis of multiple sclerosis (MS), focussing on the analysis of WML over time and correlations with other markers.

METHODS

We reviewed retrospectively the clinical, laboratory, and magnetic resonance imaging data of 21 carriers of the D313Y variant at a single German outpatient clinic for MS between 2004 and 2021.

RESULTS

In our cohort (15 females, 6 males), mean age at diagnosis was 44.1 ± 16.3 years, and mean follow-up duration was 3.1 ± 3.9 years. WML were rated on both, the Fazekas scale and the age-related white matter changes rating scale, and were of variable interindividual extent. Follow-up imaging showed virtually no progress. WML did not correlate with the severity of clinical findings or lysoGb3 levels. Symptomatic carriers of the variant are characterized by an almost complete lack of internal organ manifestations and laboratory findings, usually associated with Fabry disease.

CONCLUSION

WML in carriers of the D313Y variant do not seem to be suitable for assessing or predicting the (para-) clinical status. Concerning MS patients, the variant and its clinical signs can be a differential diagnosis, but also a co-factor. Imaging and cerebrospinal fluid findings facilitate the distinction between both entities.

Pharmacological Chaperones and Protein Conformational Diseases: Approaches of Computational Structural Biology

Whenever a protein fails to fold into its native structure, a profound detrimental effect is likely to occur, and a disease is often developed. Protein conformational disorders arise when proteins adopt abnormal conformations due to a pathological gene variant that turns into gain/loss of function or improper localization/degradation. Pharmacological chaperones are small molecules restoring the correct folding of a protein suitable for treating conformational diseases. Small molecules like these bind poorly folded proteins similarly to physiological chaperones, bridging non-covalent interactions (hydrogen bonds, electrostatic interactions, and van der Waals contacts) loosened or lost due to mutations. Pharmacological chaperone development involves, among other things, structural biology investigation of the target protein and its misfolding and refolding. Such research can take advantage of computational methods at many stages. Here, we present an up-to-date review of the computational structural biology tools and approaches regarding protein stability evaluation, binding pocket discovery and druggability, drug repurposing, and virtual ligand screening. The tools are presented as organized in an ideal workflow oriented at pharmacological chaperones' rational design, also with the treatment of rare diseases in mind.

D313Y Variant in Fabry Disease: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVES

There is accumulating evidence in the literature indicating a strong correlation between Fabry disease (FD) phenotypes and specific sequence variations in the Galactosidase Alpha (GLA) gene. Among them, the potential pathogenicity and clinical relevance of D313Y variation in patients with FD remain debated.

METHODS

We performed a systematic review and meta-analysis of studies reporting D313Y as single occurring variant in the GLA gene and sought to evaluate (1) the prevalence of D313Y variation in different populations with or without clinical manifestations of FD, (2) the clinical FD phenotype in D313Y-positive patients, and (3) the proportion of D313Y-positive patients presenting abnormal laboratory findings (alpha-galactosidase-A deficiency or globotriaosylceramide accumulation).

RESULTS

Forty cohorts comprising 211 individuals with D313Y variation among 42,723 participants with available GLA gene-sequencing data were included. Patients highly suspected for FD had a higher prevalence of D313Y variation (4.9%, 95% CI 1.6%-9.9%; I2 = 95.5%) compared with the general population (0%, 95% CI 0%-0.1%; I2 = 1.9%; p = 0.004). The prevalence of D313Y variation was 0.6% (95% CI 0.3%-1%; I2 = 74.1%), 0.4% (95% CI 0.2%-0.7%; I2 = 0%), and 0.3% (95% CI 0.2%-0.4%; I2 = 0%) in patients presenting with neurologic, cardiac, or renal manifestations, respectively. D313Y was associated with a milder, late-onset FD phenotype, as indicated by the mean patient age of 51 years (95% CI 44-59; I2 = 94%) and the evidence of alpha-galactosidase A deficiency and globotriaosylceramide accumulation in 26.7% (95% CI 15.3%-40%; I2 = 34%) and 16.2% (95% CI 8%-26.4%; I2 = 35%) of cases, respectively. D313Y-positive patients displayed predominantly neurologic FD manifestations (58.1%, 95% CI 37.7%-77.1%; I2 = 78%), with central and peripheral nervous system (CNS/PNS) involvement noted in 28.2% (95% CI 15.4%-43.2%; I2 = 51%) and 28.5% (95% CI 17.8%-40.5%; I2 = 61%) of cases, respectively.

DISCUSSION

D313Y variation seems to correlate with an atypical, mild late-onset phenotype with predominantly neurologic FD manifestations. Monitoring for CNS/PNS involvement is thus paramount to identify D313Y-positive patients with latent or early-FD pathology, which may qualify for enzyme-replacement therapy or chaperone treatment.

Fabry disease prevalence in patients with familial Mediterranean fever: A cohort study

Background/Aim: Fabry disease is an X-chromosome inherited disease, which constitutes a rare disease group. Fabry disease has a wide spectrum of symptoms and some of these symptoms that are seen in other diseases. Familial Mediterranean fever (FMF) is a common disease in countries along the Mediterranean coast, including our country. Although typical episodes of recurrent high fever and abdominal pain occur, patients can also present with nonspecific symptoms and signs. This study aimed to investigate the presence of Fabry disease in patients with FMF. Methods: Information about this cohort study was given to all patients who were followed up with a diagnosis of FMF. Those who agreed to sign the informed consent form were included in the study. Fabry disease screening was performed by galactosidase alfa (GLA) gene analysis in female patients and by examining lysosomal alpha galactosidase A (AGALA) enzyme activity in male patients. When enzyme activity was found to be low in male patients, a GLA gene analysis was also performed. Results: Fabry disease was screened in a total of 189 patients with familial Mediterranean fever, and it was not detected in any of our patients. Low AGALA enzyme activity was detected in approximately 20% of the male patients. In the GLA gene analysis performed on these patients, any genetic mutation that could be associated with Fabry disease was not detected. Conclusion: People with Fabry disease or FMF can present with common symptoms, such as arthritis, proteinuria, and abdominal pain. In our study, Fabry disease was not found in any of patients who had a diagnosis of FMF. However, only a few publications on this subject are available. In studies conducted in our country and around the world, it has been shown that GLA gene mutations that may cause Fabry disease can be detected in patients with FMF. However, such a mutation was not detected in our study.

Prevalence of Fabry Disease among Patients with Parkinson's Disease

BACKGROUND

An increased prevalence of Parkinson's disease (PD) disease has been previously reported in subjects with Fabry disease (FD) carrying alpha-galactosidase (GLA) mutations and their first-line relatives. Moreover, decreased alpha-galactosidase A (AGLA) enzymatic activity has been reported among cases with PD compared to controls.

OBJECTIVE

The aim of our study was to determine the prevalence of FD among patients with PD.

METHODS

We recruited 236 consecutive patients with PD from February 2018 to December 2020. Clinical and sociodemographic data, including the MDS-UPDRS-III scores and HY stage (the Hoehn and Yahr scale), were collected, and in-depth phenotyping was performed in subjects with identified GLA variants. A multistep approach, including standard determination of AGLA activity and LysoGb3 in males, and next-generation based GLA sequencing in all females and males with abnormal AGLA levels was performed in a routine diagnostic setting.

RESULTS

The mean age of our patients was 68.9 ± 8.9 years, 130 were men (55.1%), and the mean disease duration was 7.77 ± 5.35 years. Among 130 men, AGLA levels were low in 20 patients (15%), and subsequent Lyso-Gb3 testing showed values within the reference range for all tested subjects. In 126 subsequently genetically tested patients, four heterozygous p.(Asp313Tyr) GLA variants (3.2%, MAF 0.016) were identified; all were females. None of the 4 GLA variant carriers identified had any clinical manifestation suggestive of FD.

CONCLUSIONS

The results of this study suggest a possible relationship between FD and PD in a small proportion of cases. Nevertheless, the GLA variant found in our cohort is classified as a variant of unknown significance. Therefore, its pathogenic causative role in the context of PD needs further elucidation, and these findings should be interpreted with caution.

Screening for Fabry Disease in Kidney Transplant Recipients: Experience of a Multidisciplinary Team

Fabry disease (FD) is a rare cause of end-stage renal disease requiring kidney transplantation. Data on the incidence of unrecognized FD in kidney transplant recipients are scarce and probably underestimated. This study evaluated the incidence of FD in a population of kidney recipients, with a particular focus of the multidisciplinary approach for an early clinical assessment and therapeutic approach. Two hundred sixty-five kidney transplant recipients were screened with a genetic analysis for α-galactosidase A (GLA) mutation, with measurement of α-Gal A enzyme activity and Lyso Gb3 levels. Screening was also extended to relatives of affected patients. Seven patients (2.6%) had a GLA mutation. Two patients had a classic form of FD with Fabry nephropathy. Among the relatives, 15 subjects had a GLA mutation, and two had a Fabry nephropathy. The clinical and diagnostic assessment was completed after a median of 3.2 months, and mean time from diagnosis to treatment was 4.6 months. This study reported a high incidence of unrecognized GLA mutations in kidney transplant recipients. Evaluation and management by a multidisciplinary team allowed for an early diagnosis and treatment, and this would result in a delay in the progression of the disease and, finally, in better long-term outcomes.

Screening for Fabry Disease in Kidney Transplant Recipients: Experience of a Multidisciplinary Team

Fabry disease (FD) is a rare cause of end-stage renal disease requiring kidney transplantation. Data on the incidence of unrecognized FD in kidney transplant recipients are scarce and probably underestimated. This study evaluated the incidence of FD in a population of kidney recipients, with a particular focus of the multidisciplinary approach for an early clinical assessment and therapeutic approach. Two hundred sixty-five kidney transplant recipients were screened with a genetic analysis for α-galactosidase A (GLA) mutation, with measurement of α-Gal A enzyme activity and Lyso Gb3 levels. Screening was also extended to relatives of affected patients. Seven patients (2.6%) had a GLA mutation. Two patients had a classic form of FD with Fabry nephropathy. Among the relatives, 15 subjects had a GLA mutation, and two had a Fabry nephropathy. The clinical and diagnostic assessment was completed after a median of 3.2 months, and mean time from diagnosis to treatment was 4.6 months. This study reported a high incidence of unrecognized GLA mutations in kidney transplant recipients. Evaluation and management by a multidisciplinary team allowed for an early diagnosis and treatment, and this would result in a delay in the progression of the disease and, finally, in better long-term outcomes.