Demyelinating X-linked Charcot-Marie-Tooth disease: Unusual electrophysiological findings

X-linked Charcot-Marie-Tooth disease (CMT-X) is caused by mutations of conn exin-32 (Cx-32), which encodes a gap-junction protein. Whether the neuropat hy is primarily demyelinative or axonal remains to be established. We repor t findings of prominent demyelination in a 71-year-old woman with late-onse t disease. Electrophysiological studies revealed a nonuniform slowing of mo tor conduction velocities and dispersion of compound action potentials indi cative of a demyelinating process which was confirmed by nerve biopsy. Such electrophysiological features are unusual in hereditary neuropathies and a re more commonly found with acquired chronic demyelinating neuropathies. A systematic search confirmed the molecular genomic diagnosis of CMT-X, illus trating the value of such tests in sporadic cases. Severity of clinical sym ptoms and signs may vary with age and sex of the patient. The pathology of CMT-X in other reported cases has been variably interpreted as axonal, demy elinating, or showing both features. Our observations emphasize the demyeli native nature. (C) 1999 John Wiley & Sons, Inc.