Frequency of Fabry disease in patients with small-fibre neuropathy of unknown aetiology: a pilot study

Background: Early occurrence of small-fibre neuropathy (SFN) is a common feature of Fabry disease (FD) - an X-linked storage disorder caused by reduced activity of the alpha-galactosidase A (alpha-GAL). Although SFN may result from different disorders, the cause is often unclear. Therefore, we investigated the frequency of FD in patients with SFN of unknown aetiology. Methods: Patients with idiopathic SFN, established by sensory quantitative testing and/or skin biopsy, were examined for mutations in the alpha-GAL gene. Where mutations in the alpha-GAL gene were identified, levels of globotriaosylceramide (Gb(3)) were measured in urine and blood and the alpha-GAL activity was evaluated. When new mutations were detected, a diagnostic work-up was performed as well as a Gb(3) accumulation in the skin, lyso-Gb(3) in blood and Gb(3)_24 in urine were proved. Results: Twenty-four of 29 eligible patients were enrolled in the study. Mutations in the alpha-GAL gene were observed in five patients. A typical mutation for FD (c.424T > C, [C142R]) was detected in one patient. In four patients, a complex intronic haplotype within the alpha-GAL gene (IVS0-10C > T [rs2071225], IVS4-16A > G [rs2071397], IVS6-22C > T [rs2071228]) was identified. The relevance of this haplotype in the pathogenesis of FD remains unclear until now. However, these patients showed increased concentrations of Gb(3) and/or lyso-Gb(3), while no further manifestations for FD could be proved. Conclusions: Fabry disease should be considered in patients with SFN of unknown aetiology, and screening for FD should be included in the diagnostic guidelines for SFN. The significance of the intronic haplotype regarding SFN needs further evaluation.