• Genetics
• HMSN (charcot-marie-tooth)

Mutations in more than 50 genes cause the inherited peripheral neuropathies known as Charcot-Marie-Tooth (CMT) disease, distal hereditary motor neuropathies or hereditary sensory and autonomic neuropathies. How to diagnose these disorders is a challenge for clinicians and patients. Murphy et al have provided a simple, rational approach to this challenge in their very nice article published in last month's issue of the Journal of Neurology, Neurosurgery and Psychiatry.1 Not only were they able to evaluate over 900 patients they had personally seen in their primary inherited neuropathy clinic but also study results of more than 1000 other patients whose DNA samples had been sent to the National Hospital for genetic testing. To briefly summarise their results, 600 of the 900 patients (66%) they had personally evaluated had a primary, non-syndromic genetic neuropathy (425 CMT, 46 hereditary neuropathy with liability to pressure palsies, 61 hereditary motor neuropathies, 69 hereditary sensory and autonomic neuropathies). The 425 patients with CMT consisted of 240 patients with CMT1 (56%), 115 with CMT2 (27%) and 62 with CMT associated with intermediately slowed nerve conductions (ICMT). Ninety-two per cent of those patients with CMT and a genetic diagnosis had either a duplication of Peripheral Myelin Protein - PMP22 (CMT1A) or mutations in three other genes; MPZ (CMT1B), GJB1 (CMT1X) or MFN2 (CMT2A). If no mutation was detected with these four genes there was less than a three per cent chance of making a molecular diagnosis. This was true of course only for patients with autosomal dominant or X linked CMT although as the authors point out, many of these patients may present without a family history. For patients with clear autosomal recessive (AR) CMT …