Clinical and Molecular Features of First Mexican Friedreich's Ataxia Patients with Compound Heterozygous FXN Mutations.

Abstract

Friedreich's ataxia (FRDA) is caused by homozygous GAA repeat expansions or compound heterozygous (CH) mutations in FXN gene. Its broad clinical spectrum makes it difficult to identify, thus an accurate diagnosis can only be made by genetic testing. This study aims to present data on FXN variants observed in patients with sporadic or recessive ataxia, including detailed data of the first CH Mexican patients. One hundred and eight patients with recessive or sporadic cerebellar ataxia were referred to our institution between 2009 and 2019 for FXN molecular testing. This was achieved using a combined methodology of triplet repeat-primed PCR (polymerase chain reaction), long PCR, FXN sequencing and multiplex-ligation probe-amplification. Eighteen patients had a homozygous FXN genotype; whereas five were CH patients with a slow progression and phenotypic variability, including a late-onset case with spastic paraparesis, and a Charcot-Marie-Tooth-like case. These first Mexican CH patients pose important implications for genetic counseling and FRDA management.