Challenges in Fabry disease: the combination of two individually amenable GLA variants may be nonamenable to migalastat.

Fabry disease is a rare lysosomal storage disorder caused by mutations in the GLA gene, resulting in reduced or absent α-Gal A activity. Migalastat is an oral chaperone therapy for Fabry patients with amenable GLA variants. We previously reported a case of a 60-year-old male patient with a classic phenotype of Fabry disease, presenting with two GLA variants: p.R356Q and p.G360R. Herein, we report that, although these two missense variants are individually classified as amenable to migalastat in the validated in vitro human embryonic kidney-293 cell-based assay, their combination precludes the patient to be treated with this oral chaperone. This case illustrates how therapeutic decisions may be challenging and how a good genotypic characterization of Fabry patients is critical for the selection of the correct therapeutic strategy.

Fabry disease is a rare genetic disease that is part of a group of conditions called lysosomal storage diseases. It is characterized by an abnormal accumulation of glycosphingolipids, a subclass of glycolipids which are important components of the body's cell membranes. This accumulation is caused by a reduction in, or absence of, enzyme α-Gal A activity, which normally breaks glycosphingolipids down into smaller units, avoiding their accumulation. The absence or reduction in the α-Gal A enzyme activity is caused by mutations (changes in the normal DNA sequence) in the GLA gene. Migalastat is an oral treatment for Fabry patients with GLA mutations that respond to this treatment. We report a case of a 60-year-old male patient with Fabry disease, presenting with two GLA mutations (p.R356Q and p.G360R). Although these mutations are individually amenable to migalastat, their combination and interaction in the same chromosome precludes response to this treatment. This case illustrates how therapeutic decisions for treating Fabry disease can be challenging depending on the mutations causing the disease and how genetic material is decisive for therapy selection.

The Spanish Fabry women study: a retrospective observational study describing the phenotype of females with GLA variants.

BACKGROUND: Fabry disease (FD) is an X-linked condition caused by variants in the GLA gene. Since females have two X chromosomes, they were historically thought to be carriers. Although increased knowledge has shown that females often develop the disease, data from Spain and other countries reported that females were undertreated. The aim of this study was to provide a wider and more recent description of the disease characteristics and associated management of females with a GLA variant in a Spanish cohort. RESULTS: Ninety-seven females from 12 hospitals were included in this retrospective study. Mean age was 50.1 ± 17.2 years. Median follow-up time from GLA variant identification was 36.1 months, and most (70.1%) were identified through family screening. Variants associated with classic/non-classic phenotypes were similarly distributed (40.2%/53.6%). Missense variants were the most prevalent (n = 84, 86.6%). In the overall group, 70.4% had major organ involvement (i.e., cardiac, renal, cerebrovascular, peripheral nervous system or gastrointestinal), and 47.3% also had typical Fabry signs (angiokeratoma, cornea verticillata or increased plasma lyso-Gb3). Cardiac involvement was the most prevalent (49.5%) and the main reason for treatment initiation. A total of 33 (34%) patients received disease-specific therapy, 55% of whom were diagnosed by family screening. Females carrying variants associated with a classic phenotype had higher frequencies of clinical manifestations (92.3%) and were predominant in the treated subgroup (69.7%). Despite this, there were 34 untreated females (56.7% of total untreated), with both phenotypes represented, who had major organ involvement, with 27 of cardiac, renal or cerebrovascular nature. Age or comorbidities in this subgroup were comparable to the treated subgroup (P = 0.8 and P = 0.8, respectively). CONCLUSIONS: Efforts have been made in recent years to diagnose and treat timely Fabry females in Spain. A high percentage of females with pathogenic variants, regardless of their associated phenotype, will likely develop disease. A proportion of females with severe disease in this cohort received specific treatment. Still a significant number of females, even with same profile as the treated ones, who may be eligible for treatment according to European recommendations, remained untreated. Reasons for this merit further investigation.

Frequency of Fabry disease in a juvenile idiopathic arthritis cohort.

BACKGROUND: Fabry disease (FD) is a rare, X-linked, multisystemic lysosomal storage disorder (LSD) that results from a deficiency in the hydrolase alpha-galactosidase A (⍺-GalA). During childhood, classic FD symptomatology is rare. The majority of children may show non-specific symptoms, including in the musculoskeletal system. The prevalence of FD among juvenile idiopathic arthritis (JIA) patients is unknown. OBJECTIVE: This study aimed to identify the frequency of FD in a JIA cohort, characterizing early clinical symptoms, enzyme titers, and GLA genotyping. METHODS: Children with JIA followed in a tertiary Children Hospital cohort were selected. Clinical, laboratory and familiar information were recorded. Molecular genetic testing to detect GLA gene mutations was performed in girls and enzymatic analysis in boys. RESULTS: In 89 patients (56.2% female, age at disease onset: 8.93 ± 4.35 years), one male (1.12%) patient presented pathogenic mutation in GLA gene, c.1244 T > C p.L415P, one female patient had a variant of uncertain significance c.38C > T (p.Ala13Val). Three additional (3.4%) patients had the enzymatic activity of alpha-galactosidase slightly decreased. We observed the presence of intronic variants in 44.44% of patients in our cohort: c.1000-22C > T; c.370-81_-77del; c.640-16A > G; c.10C > T; c.548-125C > G and c.-12G > A. These variants and their combination were associated with clinical symptoms in our cohort. CONCLUSIONS: The incidence of FD in our cohort was 1.12%. Intronic variants were associated with symptoms previously described in the literature. Screening for FD in JIA may be a reasonable strategy for those with an atypical pattern of pain.

The New Pharmacological Chaperones PBXs Increase α-Galactosidase A Activity in Fabry Disease Cellular Models.

Fabry disease is an X-linked multisystemic disorder caused by the impairment of lysosomal α-Galactosidase A, which leads to the progressive accumulation of glycosphingolipids and to defective lysosomal metabolism. Currently, Fabry disease is treated by enzyme replacement therapy or the orally administrated pharmacological chaperone Migalastat. Both therapeutic strategies present limitations, since enzyme replacement therapy has shown low half-life and bioavailability, while Migalastat is only approved for patients with specific mutations. The aim of this work was to assess the efficacy of PBX galactose analogues to stabilize α-Galactosidase A and therefore evaluate their potential use in Fabry patients with mutations that are not amenable to the treatment with Migalastat. We demonstrated that PBX compounds are safe and effective concerning stabilization of α-Galactosidase A in relevant cellular models of the disease, as assessed by enzymatic activity measurements, molecular modelling, and cell viability assays. This experimental evidence suggests that PBX compounds are promising candidates for the treatment of Fabry disease caused by mutations which affect the folding of α-Galactosidase A, even for GLA variants that are not amenable to the treatment with Migalastat.

Late onset variants in Fabry disease: Results in high risk population screenings in Argentina.

BACKGROUND: Screening for Fabry disease (FD) in high risk populations yields a significant number of individuals with novel, ultra rare genetic variants in the GLA gene, largely without classic manifestations of FD. These variants often have significant residual α-galactosidase A activity. The establishment of the pathogenic character of previously unknown or rare variants is challenging but necessary to guide therapeutic decisions. OBJECTIVES: To present 2 cases of non-classical presentations of FD with renal involvement as well as to discuss the importance of high risk population screenings for FD. RESULTS: Our patients with non-classical variants were diagnosed through FD screenings in dialysis units. However, organ damage was not limited to kidneys, since LVH, vertebrobasilar dolichoectasia and cornea verticillata were also present. Lyso-Gb3 concentrations in plasma were in the pathologic range, compatible with late onset FD. Structural studies and in silico analysis of p.(Cys174Gly) and p.(Arg363His), employing different tools, suggest that enzyme destabilization and possibly aggregation could play a role in organ damage. CONCLUSIONS: Screening programs for FD in high risk populations are important as FD is a treatable multisystemic disease which is frequently overlooked in patients who present without classical manifestations.