A Rare Case of Charcot-Marie-Tooth Disease Type 1C With an Unusual Presentation.

Charcot-Marie-Tooth neuropathy type 1 (CMT1) is an inherited demyelinating neuropathy characterized by distal muscle weakness and atrophy. Charcot-Marie-Tooth disease type 1C (CMT1C) is a rare form of CMT1 caused by mutations in the lipopolysaccharide-induced tumor necrosis factor (LITAF) or small integral membrane protein of the lysosome/late endosome (SIMPLE) gene. Phenotypically, CMT1C is characterized by sensory loss and slow conduction velocity, and is typically slowly progressive and often associated with pes cavus foot deformity and bilateral foot drop. A 42-year-old female presented with a 10-year history of slowly progressive bilateral calf pain and cramps. After multiple electromyography/nerve conduction studies (EMG/NCS) and genetic testing, the patient was revealed to have CMT1C with a heterozygous pathogenic variant, c.334G>A (p.Gly112Ser). However, the presentation of the patient's CMT1C phenotype was unusual compared to patients with similar diagnosis in a previous study, including a normal sensory exam with the exception of high arches and mildly reduced vibratory sense. Additionally, the patient's teenage son already started showing symptoms of CMT1C despite the fact that the onset of the disease typically occurs at an older age. This particular case further highlights the idea that the phenotype related to CMT1C may have a wide spectrum of disease severity.