BACKGROUND:CMTX5 is characterized by peripheral neuropathy, early-onset sensorineural hearing impairment, and optic neuropathy. Only seven variants have been reported and no genotype-phenotype correlations have yet been established. PRPS1 has a crystallographic structure, as it is composed of three dimers that constitute a hexamer. METHODS:Next-generation sequencing (NGS) was performed using a custom 92-gene panel designed for the diagnosis of Charcot-Marie-Tooth (CMT) and associated neuropathies. RESULTS:We report the case of a 35-year-old male, who had presented CMT and hearing loss since childhood associated to bilateral optic neuropathy without any sign of retinitis pigmentosa. A new hemizygous variant on chromosomic position X:106,882,604, in the PRPS1 gene, c.202AÂ >Â T, p.(Met68Leu) was found. This change is predicted to lead to an altered affinity between the different subunits in the dimer, thereby may prevent the hexamer formation. CONCLUSION:CMTX5 is probably under-diagnosed, as an overlap among the different features due to PRPS1 exists. Patients who developed polyneuropathy associated to sensorineural deafness and optic atrophy during childhood should be assessed for PRPS1.
KEYWORDS: Charcot-marie-tooth, NGS, PRPS1, deafness, neuropathy