Charcot-Marie-Tooth disease

What is CMT?

Charcot-Marie-Tooth disease (CMT) is the name given to a group of conditions in which the nerves to the muscles, particularly in the lower leg and hands, don't work properly.

The part of the nerves carrying sensory signals back towards the brain may also be affected, leading to altered sensation in the affected areas.

There are two main forms of CMT. In demyelinating CMT, or CMT1, the myelin sheath that insulates and supplies nutrients to the nerves is affected. In axonal CMT, or CMT2, the nerve fibres are directly affected.

These two main types can be classified further, according to specific gene mutations and their pattern of inheritance, into at least 30 different types. However, the symptoms are similar in each type.

CMT is rare, affecting one in several thousand people.

There are many different genetic variants. Most cases are inherited as an autosomal dominant condition, but some are inherited in an autosomal recessive or x-linked pattern.

Symptoms of CMT

Some of those with CMT1 never develop symptoms.

When symptoms do appear, the first sign is usually a difficult with walking. The peroneal muscles on the outer side of the calves are usually affected first, leading to wasting and weakness of the leg and foot drop.

Legs have a characteristic shape - an inverted champagne bottle, with normal thigh muscle bulk but very thin lower legs. Sensation becomes diminished and reflexes reduced.

Symptoms spread to the hands, then the arms. Weakness of these muscles makes everyday functioning difficult, as strength and dexterity are reduced.

Numbness of the hands and feet develops and, in extreme cases, can lead to injuries that go unnoticed.

Cold feet and hands are a frequent complaint. Occasionally, there's also a tremor or curvature of the spine.

Progress of the disease is usually slow and many people are only mildly affected. Up to 20 per cent have no symptoms at all and are only picked up on electrical nerve tests.

However, in some cases CMT can be totally incapacitating, with patients losing the ability to walk.

Diagnosing CMT

Diagnosis can be established with a combination of electrical nerve tests (where abnormalities may be seen from the age of five years) and genetic tests on blood.

Screening during pregnancy is possible using CVS in those families where a genetic problem has been identified.

Treatment of CMT

There is no cure for CMT, but supportive treatments can improve some symptoms.

Advice and support

CMT United Kingdom

• Tel: 0800 652 6316
• Website: www.cmt.org.uk