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GJB1 gene mutations in suspected inflammatory demyelinating neuropathies not responding to treatment
  1. A W Michell1,
  2. M Laura2,
  3. J Blake1,2,4,
  4. M P Lunn2,
  5. A Cox5,
  6. V S Gibbons3,
  7. M B Davis3,
  8. N W Wood3,
  9. H Manji2,
  10. H Houlden2,
  11. N M F Murray1,
  12. M M Reilly2
  1. 1
    Department of Clinical Neurophysiology, The National Hospital for Neurology and Neurosurgery and Department of Molecular Neuroscience, Institute of Neurology, London, UK
  2. 2
    MRC Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery and Department of Molecular Neuroscience, Institute of Neurology, London, UK
  3. 3
    Neurogenetics Laboratory, The National Hospital for Neurology and Neurosurgery and Department of Molecular Neuroscience, Institute of Neurology, London, UK
  4. 4
    Department of Clinical Neurophysiology, Norfolk and Norwich University Hospital, Norwich, UK
  5. 5
    Department of Clinical Neuroscience, Addenbrooke’s Hospital, Cambridge, UK
  1. Dr M M Reilly, MRC Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery and Department of Molecular Neuroscience, Institute of Neurology, Queen’s Sq, London WC1N 3BG, UK; m.reilly{at}ion.ucl.ac.uk

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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.14 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 reports

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 …

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