Novel mutation in the MPZ gene causes early-onset but slow-progressive Charcot–Marie–Tooth disease in a Russian family: a case report

Abstract

Charcot–Marie–Tooth disease (CMT) is a genetically heterogeneous group of peripheral neuropathies most of which are associated with mutations in four genes including peripheral myelin protein-22 ( PMP22), myelin protein zero ( MPZ), gap junction protein beta1 ( GJB1) and mitofusin2 ( MFN2). This current case report describes the clinical and genetic characteristics of a 6-year-old male proband. A physical examination revealed muscular hypotonia. He started walking on his own at 18 months. A nerve conduction study with needle electromyography revealed conduction block. A novel MPZ mutation (c.398C > T, p.Pro133Leu) was revealed in the proband. This mutation was also found in the 32-year-old father of the proband. The father had had deformity of the feet and distal muscle weakness since childhood. The novel p.Pro133Leu pathogenic mutation was responsible for early onset but slowly progressive CMT1B. We assume that this site is an intolerant to change region in the MPZ gene. This variant in the MPZ gene is an important contributor to hereditary neuropathy with reduced nerve conduction velocity in the Russian population. This case highlights the importance of whole exome sequencing for a proper clinical diagnosis of CMT associated with a mutation in the MPZ gene.