A genotyping study of 13 cases of early-onset Charcot-Marie-Tooth disease

Abstract:

Objective To study the clinical characteristics and genetic variation of early-onset Charcot-Marie-Tooth disease (CMT). Methods Children with a clinical diagnosis of early-onset CMT were selected for the study. Relevant clinical data were collected, and electromyogram and CMT-related gene detection were performed and analyzed. Results A total of 13 cases of early-onset CMT were enrolled, including 9 males (69%) and 4 females (31%). The mean age at consultation was 4.0±2.1 years. Among them, 12 children (92%) had an age of onset less than 2 years, 9 children (69%) were diagnosed with CMT type 1 (including 6 cases of Dejerine-Sottas syndrome), 1 child (8%) with intermediate form of CMT, and 3 children (23%) with CMT type 2. The genetic test results of these 13 children showed 6 cases (46%) of PMP22 duplication mutation, 3 cases (23%) of MPZ gene insertion mutation and point mutation, 3 cases (23%) of MFN2 gene point mutation, and 1 case (8%) of NEFL gene point mutation. Eleven cases (85%) carried known pathogenic mutations and 2 cases (15%) had novel mutations. The new variant c.394C > G (p.P132A) of the MPZ gene was rated as "possibly pathogenic" and the new variant c.326A > G (p.K109R) of the MFN2 gene was rated as "pathogenic". Conclusions Early-onset CMT is mainly caused by PMP22 gene duplication mutation and MPZ gene mutations. The clinical phenotype is mainly CMT type 1, among which Dejerine-Sottas syndrome accounts for a considerable proportion.