Charcot-Marie-Tooth disease type 2F associated with biallelic HSPB1 mutations

Objective: This work aims to expand knowledge regarding the genetic spectrum of HSPB1-related diseases. HSPB1 is a gene encoding heat shock protein 27, and mutations in HSPB1 have been identified as the cause of axonal Charcot-Marie-Tooth (CMT) disease type 2F and distal hereditary motor neuropathy (dHMN). Methods: Two patients with axonal sensorimotor neuropathy underwent detailed clinical examinations, neurophysiological studies, and nextgeneration sequencing with subsequent bioinformatic prioritization of genetic variants and in silico analysis of the likely causal mutation. Results: The HSPB1 p.S135F and p.R136L mutations were identified in homozygosis in the two affected individuals. Both mutations affect the highly conserved alpha-crystallin domain and have been previously described as the cause of severe CMT2F/ dHMN, showing a strictly dominant inheritance pattern. Interpretation: Thus, we report for the first time two cases of biallelic HSPB1 p.S135F and p.R136L mutations in two families.