Charcot-Marie-Tooth disease type 1 (CMT1, hereditary sensorimotor polyneuropathy type-1, HSMN1)

Introduction

Demyelinating polyneuropathy.

Epidemiology

• most common hereditary neuropathy

Pathology

• abnormal myelin formation
• Schwann cell proliferation

Genetics

• autosomal dominant
• most kindreds have a duplication at 17p11.2

Clinical manifestations

(also see Charcot-Marie-Tooth disease)

• slowly progressive distal muscle atrophy & weakness
• absent deep tendon reflexes
• high arched feet & palate may be present
• hammer toes
• palpably enlarged peripheral nerves

Laboratory

• CMT1 gene mutation

Diagnostic procedures

• nerve conduction studies:
  • decreased nerve conduction velocity characteristic of demyelinating neuropathy (50% of normal conduction velocity) (< 38 m/s)
  • diagnostic test of choice
  • few other disorders show this degree of nerve conduction velocity slowing
• electromyography:
  • enlarged motor unit potential
  • reduced recruitment
  • fibrillation potentials not prominent
• muscle biopsy shows chronic denervation, a non-specific finding

More general terms

• Charcot-Marie-Tooth disease

More specific terms

• Charcot-Marie-Tooth disease type 1A; hereditary motor & sensory neuropathy 1A (CMT1A)
• Charcot-Marie-Tooth disease type 1B (CMT1B)
• Charcot-Marie-Tooth disease type 1C (CMT1C)
• Charcot-Marie-Tooth disease type 1D (CMT1D)
• Charcot-Marie-Tooth disease type 1E (CMT1E)
• Charcot-Marie-Tooth disease type 1F (CMT1F)
• Charcot-Marie-Tooth disease type 1X (CMTX)

Patient information

Charcot-Marie-Tooth disease type 1 patient information