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What is Charcot-Marie-Tooth Disease (CMT)


Charcot-Marie-Tooth disease (CMT) is one of the most common inherited neurological disorders, also known as hereditary motor and sensory neuropathy (HMSN) or peroneal muscular atrophy, it comprises a group of disorders that affect peripheral nerves. The peripheral nerves lie outside the brain and spinal cord and supply the muscles and sensory organs in the limbs.

Symptoms of Charcot-Marie-Tooth Disease
T
he neuropathy of CMT affects both motor and sensory nerves. A typical feature includes weakness of the foot and lower leg muscles, which may result in foot drop and a high-stepped gait with frequent tripping or falls. Foot deformities, such as high arches and hammertoes (a condition in which the middle joint of a toe bends upwards) are also characteristic due to weakness of the small muscles in the feet. In addition, the lower legs may take on an "inverted champagne bottle" appearance due to the loss of muscle bulk. Later in the disease, weakness and muscle atrophy may occur in the hands, resulting in difficulty with fine motor skills.

Onset of symptoms is most often in adolescence or early adulthood, however presentation may be delayed until mid-adulthood. The severity of symptoms is quite variable in different patients and even among family members with the disease. Progression of symptoms is gradual. Pain can range from mild to severe, and some patients may need to rely on foot or leg braces or other orthopedic devices to maintain mobility. Although in rare cases patients may have respiratory muscle weakness, CMT is not considered a fatal disease and people with most forms of CMT have a normal life expectancy.

Causes
A nerve cell communicates information to distant targets by sending electrical signals down a long, thin part of the cell called the axon. In order to increase the speed at which these electrical signals travel, the axon is insulated by myelin, which is produced by another type of cell called the Schwann cell. Myelin twists around the axon like a jelly-roll cake and prevents dissipation of the electrical signals. Without an intact axon and myelin sheath, peripheral nerve cells are unable to activate target muscles or relay sensory information from the limbs back to the brain.


 

Charcot-Marie-Tooth Disease (CMT)

Name of Group

 

TBC

 

Short description

 

TBC
 

Contact Details

 

TBC
 

Name of Group

 

CMT United Kingdom

 

Web Address

 

www.cmt.org.uk

 

Contact Details

 

0800 652 6316

 

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CMT is caused by mutations in genes that produce proteins involved in the structure and function of either the peripheral nerve axon or the myelin sheath. Although different proteins are abnormal in different forms of CMT disease, all of the mutations affect the normal function of the peripheral nerves. Consequently, these nerves slowly degenerate and lose the ability to communicate with their distant targets. The degeneration of motor nerves results in muscle weakness and atrophy in the extremities (arms, legs, hands, or feet), and in some cases the degeneration of sensory nerves results in a reduced ability to feel heat, cold, and pain.

The gene mutations in CMT disease are usually inherited. Each of us normally possesses two copies of every gene, one inherited from each parent. Some forms of CMT are inherited in an autosomal dominant fashion, which means that only one copy of the abnormal gene is needed to cause the disease. Other forms of CMT are inherited in an autosomal recessive fashion, which means that both co
pies of the abnormal gene must be present to cause the disease.

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