Identification of Four New Mutations in the GLA Gene Associated with Anderson-Fabry Disease

Anderson-Fabry disease is a hereditary, progressive, multisystemic lysosomal storage disorder caused by a functional deficiency of the enzyme α-galactosidase A (α-GalA). This defect is due to mutations in the GLA gene, located in the long arm of the X chromosome (Xq21-22). Functional deficiency of the α-GalA enzyme leads to reduced degradation and accumulation of its substrates, predominantly globotriaosylceramide (Gb3), which accumulate in the lysosomes of numerous cell types, giving rise to the symptomatology. Clinical diagnosis can still be difficult today due to the peculiarities of the disease, which presents with clinical manifestations that overlap with those of other pathologies and a wide possibility of differential diagnoses, which lead to missed diagnoses, misdiagnosis, or a diagnostic delay. Patients with clinical suspicion of Fabry disease undergo a diagnostic workup that includes an evaluation of α-GALA enzyme activity, genetic analysis of the GLA gene, and the measurement of blood Lyso-Gb3, a soluble derivative of Gb3. In this paper, we describe four novel mutations identified in the GLA gene which are associated with absent or reduced α-GalA activity, pathological accumulation of the specific substrate, and characteristic clinical manifestations of Fabry disease. We identified two mutations (c.583insGAATA and p.Y207X) that result in the formation of a premature translation stop codon, resulting in a truncated protein and thus a completely non-functional enzyme. The other two identified gene alterations (p.G261C and c.786G>T, which determine p.W262C) are missense mutations that cause reduced α-GALA activity, the accumulation of blood Lyso-Gb3, and symptoms consistent with Fabry disease, and therefore may be associated with this disorder. The identification of these new mutations in patients with symptoms attributable to Fabry disease increases the molecular knowledge of the GLA gene and provides important support to the clinician, for a more accurate and timely diagnosis of the pathology.