What is Charcot-Marie-Tooth disease?

Charcot-Marie-Tooth disease (CMT) is named after the three neurologists who first described the condition in 1886.  The other term commonly used to describe the condition is hereditary motor and sensory neuropathy (HMSN). This name describes the two primary features of this condition: it is hereditary (passed on in the genes from parent to child) and it affects the motor and sensory peripheral nerves. CMT is not in fact a single disorder but a group of conditions that share some similarities.

What causes Charcot-Marie-Tooth disease?

Researchers have identified a number of genes in which mutations are known to cause CMT. These mutations usually affect the production of a particular protein in the peripheral nerves, either causing the protein to be faulty or not produced at all which leads to peripheral nerve damage.

CMT is a hereditary disease in which the genetics are very complicated; the disease has different inheritance patterns for different types of CMT. Most sub-types of CMT type 1 are inherited in an autosomal dominant manner – this means that you only need to inherit the faulty gene from one parent to have the condition. CMT X1 is the only exception in the type 1 category: it has X-linked inheritance, which means it is determined by a gene carried on the X chromosome. As males have only one X chromosome, and females have two, males tend to be much more severely affected by CMT X1 than females.

Although most sub-types of CMT type 2 are autosomal dominant, there are a few rare sub-types that are inherited in an autosomal recessive manner. This means that you need to inherit the faulty gene from both parents to have the condition.

What are the signs and symptoms of Charcot-Marie-Tooth disease?

In the more common types of CMT, the first symptoms usually occur in the first decade of life, however, in other types, symptoms may not appear until much later. Many people with CMT have high arched feet (known as pes cavus) which becomes particularly noticeable at the time of the growth spurt associated with puberty. Some people have weakness in their hands, but this does not usually cause symptoms until after the age of 20.

People can experience numbness in their feet and hands and having cold feet is quite common too. Many patients with CMT eventually develop contractures (stiffened joints) that result in deformities of the feet and hands.

How does the disease progress?

The types of CMT which run through the generations are very slowly progressive. It is unusual for people with CMT to lose the ability to walk, although some people – especially when they are older – may need to a walking aid. The severity of the condition is highly variable, but the condition only rarely leads to severe disability.