Charcot Marie Tooth disease, more usefully known as hereditary motor and sensory neuropathy (HMSN), is the most common group of genetic peripheral neuropathies. There are over 40 different genes known to be directly associated with CMT, the most common being an autosomal dominant mutation in the peripheral myelin protein 22 gene (PMP22).

Autosomal dominant inheritence

There are two broad groups of disease:

• type 1 which is a demyelinating condition which is more common (and includes the PMP22 subtype)
• type 2 which is axonal.

The disease is length-dependent, meaning that patients present (usually in puberty) with symptoms affecting the feet, later progressing to involve the hands (usually as the knees become involved).

Features

muscle weakness + neuropathy (motor problems are more prominent clinically)

• There may be a history of frequently sprained ankles
• Foot drop
• High-arched feet (pes cavus)
• Hammer toes
• Distal muscle weakness
• Distal muscle atrophy - champage bottle legs are observed in CMT type 1
• Hyporeflexia
• Stork leg deformity