Charcot-Marie-Tooth Disease
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Introduction

An inherited peripheral neuropathy. Various forms of inheritances, the most common is autosomal dominant. Can also be passed on in autosomal recessive and X-linked patterns. In rare instances it may be sporadic.

Sometimes called hereditary motor and sensory neuropathy (HMSN), or peroneal muscular atrophy.

Presentation

  • Usually in puberty, can be between the ages of 10 and 30
  • Progressive distal muscle weakness and wasting
  • Foot drop / high stepping / foot slapping gait
  • Hammer toe – the toes are always curled
  • Variable loss of reflexes and other sensory signs
  • May progress to hands, arms and face later in the disease. Changes in the arms are similar to those seen in the legs, and occur later in the disease.
    • In some, the diaphragm may be affected, making breathing difficult
    • Rarely it may affect vision, hearing and balance
  • Pes cavus – an exaggerated arch of the foot – develops over time
  • Reduced mobility over time
  • Normal tone, but slight reduced power – although strength normally remains reasonable
  • Prevalence – 37 per 100 000 (roughly 1 in 2500)
  • Champagne bottle legs appearance – as the result of peroneal muscle wasting, the legs appear like inverted champagne bottles
  • Often disabling, but rarely causes total paralysis
  • May respond to surgery
  • Patients may have scars across the dorsum of the toes, and under the arch of the foot, where they have had corrective surgery for foot deformities.
Charcot Marie Tooth Foot
Charcot Marie Tooth Foot. Note the high arch, hammer toe and reduced muscle. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Pathology

The result of dysfunctional genes that code for proteins in the myelin sheath (Type I), or more rarely in the axonal mirochondria of the nerve fibre itself (Type II), resulting in damage to the myelin sheath, and altered nerve transmission as a result of this damage.
Demonstration of nerve conduction in Charcot-Marie-Tooth
Demonstration of nerve conduction in Charcot-Marie-Tooth. Neurone on the right shows normal conduction. Neurone on the left shows “Saltatory Conduction” as a result of loss of the myelin sheath as seen in Charcot-Marie-Tooth. This file is taken from wikimedia commons and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Management

There is no cure, and there is very little treatment.
  • Patients advised to stay active, and do exercise
  • Hydrotherapy may help
  • Advised to keep weight low, to reduce the risk of mobility problems
  • Trails on the use of ascorbic acid (vit C) are underway to assess its efficacy
  • Genetic testing can reveal if children and relatives are at risk
  • Surgery can reduce deformity (e.g. of clawed toes and pes cavus)

References

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) currently works as a GP Registrar and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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