Unusual electrophysiological findings in X-linked dominant Charcot-Marie-Tooth disease.

X-linked Charcot-Marie-Tooth disease (CMTX) is the second most common form of Charcot-Marie-Tooth disease. Variable histopathological and nerve conduction velocity (NCV) results have suggested either a primary demyelinating or axonal polyneuropathy. We identified five individuals across three generations in a family with CMTX associated with a mutation in the gene coding for connexin 32. All individuals were studied by clinical neurological examination, DNA analysis, and nerve conduction studies. The proband (1174/KD) also underwent a sural nerve biopsy. As expected, all the affected males were more clinically affected than the females. All affected males and obligate female carriers exhibited some electrophysiological characteristics of demyelination. However, striking heterogeneity of nerve conduction velocities was seen. This family shows that CMTX is a heterogeneous and distinctly nonuniform demyelinating polyneuropathy, the severity of which varies with sex and age. Such electrophysiological variability is unique among hereditary neuropathies.