Early renal failure in childhood in a male with Fabry disease.

Fabry disease is an X-linked lysosomal storage disorder caused by reduced activity or absence of the alpha-galactosidase A enzyme resulting in systemic accumulation of glycosphingolipids. End-stage renal disease (ESRD) is a late-stage manifestation of Fabry disease, typically presenting in the fifth decade of life, but is very rare in childhood. Here we present a case of an 11-year-old boy with classical Fabry disease presenting with ESRD requiring haemodialysis and transplant. Diagnosis was confirmed by renal biopsy, GLA mutation and low alpha-galactosidase A levels. He has an unusual genotype, hemizygous for the c.1000-11T>A intronic variant and positive for the pseudodeficiency allele D313Y. Due to the possibility of very early and accelerated disease progression, Fabry disease should be considered as a possible diagnosis in unexplained renal failure in males from a younger age.

A variant of unknown significance in the GLA gene causing diagnostic uncertainty in a young female with isolated hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is genetically heterogeneous, and largely caused by mutations in genes encoding sarcomere proteins. However, GLA mutations causing Fabry disease, an X-linked lysosomal storage disorder, may also present with isolated HCM. As HCM genetic testing panels are increasingly being used clinically, variants of unknown significance (VUS) are encountered, leading to challenges in interpretation. We present an illustrative case: a 10-year-old girl with isolated HCM who, on testing with a HCM multi-gene panel, was found to carry a maternally inherited p.W24R variant in GLA. Attempts to evaluate the significance of this variant, by direct biochemical testing of patient specimens, gave inconclusive results. Subsequent in vitro protein expression studies suggested that the variant is unlikely to be pathogenic. This case highlights diagnostic dilemmas that can be provoked by VUS in general, and specifically raises a question whether GLA sequencing should be included in first-line diagnostic testing for female children with isolated hypertrophic cardiomyopathy.

Functional analysis of variant lysosomal acid glycosidases of Anderson-Fabry and Pompe disease in a human embryonic kidney epithelial cell line (HEK 293 T).

The functional significance of missense mutations in genes encoding acid glycosidases of lysosomal storage disorders (LSDs) is not always clear. Here we describe a method of investigating functional properties of variant enzymes in vitro using a human embryonic kidney epithelial cell line. Site-directed mutagenesis was performed on the parental plasmids containing cDNA encoding for alpha-galactosidase A (α-Gal A) and acid maltase (α-Glu) to prepare plasmids encoding relevant point mutations. Mutant plasmids were transfected into HEK 293 T cells, and transient over-expression of variant enzymes was measured after 3 days. We have illustrated the method by examining enzymatic activities of four unknown α-Gal A and one α-Glu variants identified in our patients with Anderson-Fabry disease and Pompe diseases respectively. Comparison with control variants known to be either pathogenic or non-pathogenic together with over-expression of wild-type enzyme allowed determination of the pathogenicity of the mutation. One leader sequence novel variant of α-Gal A (p.A15T) was shown not to significantly reduce enzyme activity, whereas three other novel α-Gal A variants (p.D93Y, p.L372P and p.T410I) were shown to be pathogenic as they resulted in significant reduction of enzyme activity. A novel α-Glu variant (p.L72R) was shown to be pathogenic as this significantly reduced enzyme activity. Certain acid glycosidase variants that have been described in association with late-onset LSDs and which are known to have variable residual plasma and leukocyte enzyme activity in patients appear to show intermediate to low enzyme activity (p.N215S and p.Q279E α-Gal A respectively) in the over-expression system.

Prevalence of Anderson-Fabry disease in patients with hypertrophic cardiomyopathy: the European Anderson-Fabry Disease survey.

OBJECTIVES: The prevalence of Anderson-Fabry disease (AFD) in patients presenting with unexplained left ventricular hypertrophy (LVH) is controversial. The aim of this study was to determine the prevalence of AFD in a large, consecutive cohort of patients with hypertrophic cardiomyopathy (HCM) using rapid mutation screening. DESIGN, SETTING AND PATIENTS: A European multicentre cross-sectional study involving 13 referral centres. Inclusion criteria for the study were: men aged at least 35 years and women aged at least 40 years with unexplained LVH (maximum left ventricular wall thickness ≥ 1.5 cm). All patients were screened using a denaturing high-performance liquid chromatography protocol for rapid mutation screening of the α-galactosidase A (α-Gal A) gene and, if a sequence variant was found, direct sequencing was performed. 1386 patients (63.9% men, mean age 57.9 ± 12.0 years) were enrolled in the study. RESULTS: Seven (0.5%) patients (age 57.4 ± 9.0 years (45-72); three (43%) men) had pathogenic α-galactosidase A mutations. Polymorphisms were identified in 283 patients (20.4%). Maximal left ventricular wall thickness in patients carrying a disease-causing mutation was 18 ± 2 mm (range 15-22); four patients had concentric LVH and the remainder had asymmetric septal hypertrophy. CONCLUSIONS: The prevalence of AFD gene mutations in a large, consecutive cohort of European patients with unexplained LVH is 0.5%.

Clinical expression of plakophilin-2 mutations in familial arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disorder characterized by loss of cardiomyocytes and their replacement by adipose and fibrous tissue. It is considered a disease of cell adhesion because mutations in desmosomal genes, desmoplakin and plakoglobin, have been implicated in the pathogenesis of ARVC. In a recent report, mutations in plakophilin-2, a gene highly expressed in cardiac desmosomes, have been shown to cause ARVC. METHODS AND RESULTS: We investigated 100 white patients with ARVC for mutations in plakophilin-2. Nine different mutations were identified by direct sequencing in 11 cases. Five of these mutations are novel (A733fsX740, L586fsX658, V570fsX576, R413X, and P533fsX561) and predicted to cause a premature truncation of the plakophilin-2 protein. Family studies showed incomplete disease expression in mutation carriers and identified a number of individuals who would be misdiagnosed with the existing International Task Force and modified diagnostic criteria for ARVC. CONCLUSIONS: In this study, we provide new evidence that mutations in the desmosomal plakophilin-2 gene can cause ARVC. A systematic clinical evaluation of mutation carriers within families demonstrated variable phenotypic expression, even among individuals with the same mutation, and highlighted the need for a more accurate set of diagnostic criteria for ARVC.