Charcot -Marie -Tooth disease is a group of neuromuscular disorders that primarily affect the peripheral nerves that connect the spinal cord and brain to the muscles and sensory organs.
Charcot -Marie-Tooth disease affects neurons or nerve cells that communicate the information to various points through electrical signals through a long thin part of the cell called the axon. To increase the speed of these electric signals, the axon is covered with a substance called myelin. Myelin is wrapped around the axon preventing the dissipation of the electrical signals. If the axons and myelin sheaths present problems, peripheral nerve cells cannot activate muscles correctly or transmit sensory information from the limbs to the brain.
The main symptoms of Charcot- Marie -Tooth disease are muscle weakness and loss of sensation in the extremities of the body: feet, lower legs, hands and forearms.
This disorder usually occurs in adolescence or early adulthood, but can start at any time from infancy to late adulthood. The first symptoms of Charcot -Marie -Tooth muscular weakness usually appears in the feet that can cause abnormalities such as pes cavus, wherein the foot has a steeper than normal or hammertoes arch, and an abnormal curvature of the fingers feet. As the disease progresses, the muscles in the lower legs and ankles often develop debilitating muscle weaknesses in the hands occur. People with this disorder may also experience pain or burning in the feet and lower legs or even decreased sensation to touch, heat and cold. In rare cases this loss of sensitivity can lead to loss of hearing or vision. The symptoms of this disease can vary in severity even in individuals of the same family, but this disorder does not usually affect life expectancy in most patients.
MT symptoms vary greatly in each individual. No doctor can predict how you will be in 10 or 20 years. How CMT expresses itself depends on your lifestyle, the activities you undertake, stresses that are created due to everyday life, the diet you have during your lifetime and everything you do in your life. Since no two people are the same, each CMT is different. There are elderly carriers of CMT who lead an active life without setbacks. Hence, many CMT carriers do not know they have this disease.
Patients with type 1 CMT usually debut during mid-childhood and present insidiously progressive atrophy that usually starts with the distal portion of the body such as legs and arms, which ends up in a deformity usually referred to "stork leg" later on in life, atrophy of the intrinsic muscles of the hand starts. There is a decrease of the pain, vibration and heat sensitivity, with distribution in the area of the hands and feet. Tendon and muscle reflexes are lost. Deformities of the feet with high arches pedis or hammer toes may be the only manifestations in individuals with family carriers of the trait. Patients with type 1 CMT have slow nerve conduction speeds with prolonged distal latencies. Pathological samples show demyelination and remyelination of the nerves. Enlarged nerves in the distal portion of the body can be present to the touch. The disease progresses slowly and is compatible with a normal life span. Clinically, patients with type 2 CMT usually debut with weakness in a later stage of lifeF, and the evolution of the process is even slower. The nerve conduction speeds in patients are relatively normal, but evoked potentials are of low amplitude and biopsies reveal a Wallerian degeneration.
Type 3 CMT, which is also known as Hypertrophic interstitial neuropathy (Dejerine- Sottas), is a rare and recessive disorder of the peripheral nerves, which appears during childhood and develops into progressive weakness and sensory impairment, with loss of deep tendon reflexes. This disease initially resembles Charcot- Marie –Tooth disease, but the motor weakness symptom progresses faster. It is also a demyelinating disorder with remyelination, with similar peripheral enlargement of the nerves and a characteristic shape called "onion bulbs" that are seen during biopsies.
Some people with CMT also experience problems with proprioception which is nothing but the ability to tell where your body is placed in the space around it.
With early diagnosis and taking the necessary care, most people with CMT will live a normal life without much difficulty, although there is no denying the fact that some people have severe debilitating problems throughout their lives. Life expectancy is not usually shortened.
CMT is caused by defects in genes that affect the functioning of peripheral nerves. Genes provide the instructions or maps for proteins in the body. When a gene is abnormal, the protein is also altered. The genes that cause CMT are altered and affect either fiber or nerve myelin layers around them which are created by proteins.
Three genes have been identified in patients with type 1 CMT. These genes are located in chromosomes 1, 17 and they are not related to the sex of the person, so they seem to be connected to X.
The only known main risk for CMT is having someone in the family previously diagnosed with the disease.