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It is generally accepted that while inflammatory demyelinating neuropathies often cause patchy demyelination resulting in conduction block, temporal dispersion and variation in conduction velocities, demyelinating hereditary neuropathies such as Charcot–Marie–Tooth (CMT) disease type 1A are usually characterised by homogeneous slow conduction.
X-linked CMT is caused by mutations in the gap junction beta 1 (GJB1) gene encoding connexin 32, a gap junction protein, resulting in intermediate conduction velocities. At our institution, mean median nerve conduction velocity in men with GJB1 mutations is 33.2 ± 7.5 m/s (n = 13) and 47.7 ± 7.0 m/s in women (n = 8), similar to other recent series.1 2 There is increasing evidence that nerve conduction is not always homogeneous in GJB1 associated CMT.1–4 Here we present three cases in which the neurophysiology suggested an inflammatory demyelinating neuropathy, but who failed to respond to treatment and were subsequently found to have mutations in GJB1.
Case No 1
A 23-year-old man presented with parasthesia affecting both feet that progressed to mild hand parasthesia and weakness over 6 months. Although slightly clumsy, he had been good at sport as a teenager. He had minimal wasting but normal power in his hands, he was areflexic and had reduced vibration and pinprick distally. CSF was acellular, with a raised protein of 0.78 g/l. His initial nerve conduction studies (NCS) (done elsewhere) suggested chronic …
Funding: We acknowledge the Medical Research Council and the Muscular Dystrophy Campaign for funding support. This work was undertaken at University College London Hospitals/University College London, which received a proportion of funding from the Department of Health’s National Institute for Health Research Biomedical Research Centres funding scheme.
Competing interests: None.
Patient consent: Obtained.
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