Electrophysiological findings in SH3TC2 neuropathy mimicking inflammatory neuropathies

Biallelic SH3TC2 variants lead to autosomal recessive Charcot-Marie-Tooth type 4C (CMT4C) which is typically demyelinating and associated with early-onset spinal deformities. Electrophysiology typically reveals a non-uniform conduction velocity (CV) slowing, a pattern traditionally linked to inflammatory neuropathies, potentially leading to diagnostic misinterpretation.

Clinical and neurophysiological data from 19 patients belonging to 16 unrelated families with confirmed CMT4C were retrospectively collected across six neuromuscular reference centres in Brazil.

Among the 19 patients, consanguineous parentage was found in 11 patients. Most patients exhibited symptom onset before age 10, and difficulty walking was the most common presenting symptom. A high rate of initial misdiagnosis was noted, with six patients initially diagnosed as inflammatory neuropathy. Proximal muscle weakness since initial assessment, present in 13 patients, and non-uniform CV slowing, present in all patients, contributed to this diagnostic misinterpretation.

This is the largest Brazilian cohort of patients with CMT4C to date. Key findings include frequent non-uniform CV slowing, excessive temporal dispersion and a high rate of misdiagnosis, often as acquired demyelinating neuropathy. Clinicians should be aware of the distinctive neurophysiological pattern of SH3TC2-related neuropathy to avoid misdiagnosis, unnecessary ancillary tests and treatment.