Anderson–Fabry Disease Homozygosity: Rare Case of Late-Onset Variant

Abstract

Anderson–Fabry Disease (AFD) is a rare, X-linked lysosomal storage disorder caused by a mutation in the α-Galactosidase A gene resulting in α-Galactosidase A enzyme (α-Gal A) deficiency. The metabolic defect leads to the progressive accumulation of glycosphingolipids and the structural and functional impairment of affected organs. Due to the inheritance pattern, male patients are hemizygous with more severe manifestations of the disease as compared to females who, in most cases, are heterozygous with delayed and variable clinical presentation caused by uneven X-chromosome inactivation. Fabry disease cases are often identified by targeted screening programs in high-risk groups, such as in patients with end-stage renal disease, premature stroke, or unexplained cardiomyopathy. Here, we describe a unique case of a homozygous female patient identified by a nationwide screening program in hypertrophic cardiomyopathy patients. Before the systematic screening, the patient had a diagnosis of hypertrophic obstructive cardiomyopathy and was treated accordingly, including with alcohol septal ablation to reduce the obstructive gradient. The confirmation of Fabry disease led to the discovery of the same variant in several members of her family. The identified variant was c.644A>G, p.Asn215Ser (p.N215S), which is known to cause predominant cardiac involvement with late onset of the disease. This variant is amenable to oral therapy with the small-molecule chaperone migalastat, which was started and then interrupted due to the recurrence of the patient’s migraine and then re-initiated again after two years. During this period, the patient received enzyme replacement therapy with agalsidase beta but developed progressively worsening venous access. Our case illustrates the importance of the systematic screening of patients with clinical evidence of hypertrophic cardiomyopathy in whom the routine diagnostic process fails to discover Fabry disease, in particular variants with late-onset cardiac manifestations. Many of the late-onset variants are amenable to orally active therapy with migalastat, which significantly improves the comfort of the treatment. Its long-term results are being analyzed by a large international “Follow-me” registry, which was designed to verify the validity of pivotal trials with migalastat in Fabry disease.

Keywords

• case report
• Anderson–Fabry disease
• homozygosity
• exon 5
• late onset