Charcot Marie Tooth Disease
By Drs. Li-Ke Wu, Xiaojuan Wang, Bo Cheng, Susan Chu, Shuangshuang Liu and Xiang Wang
Wu Medical Center, Bejing, China
Charcot-Marie-Tooth disease is a group of hereditary disorders that damage the nerves in the arms and legs (peripheral nerves). Charcot-Marie-Tooth is also known as hereditary motor and sensory neuropathy.
The main signs and symptoms of Charcot-Marie-Tooth disease are muscle weakness and decreased muscle size. Patients may also notice a decreased sensation in those areas affected by the disease. Foot deformities such as hammertoes and high arches are common for patients suffering from Charcot-Marie-Tooth disease. Symptoms usually begin in the feet and legs, and they may eventually affect the hands and arms.
Muscle weakness and loss of balance can make walking difficult. Symptoms of Charcot-Marie-Tooth disease typically appear during adolescence or early adulthood, but this condition can develop during midlife as well.
Symptoms
Signs and symptoms of Charcot-Marie-Tooth disease may include:
Weakness in the legs, ankles and feet
Loss of muscle bulk in the legs and feet
High foot arches
Curled toes (hammertoes)
Decreased ability to run
Difficulty lifting the foot at the ankle (footdrop)
Awkward or higher than normal step (gait)
Frequent tripping or falling
Decreased sensation or a loss of feeling in the legs and feet
As Charcot-Marie-Tooth disease progresses, symptoms may not be limited to the feet and legs but may also involve the hands and arms. The severity of the symptoms can vary greatly from person to person. This is true even among family members.
Causes
Charcot-Marie-Tooth disease is a group of related conditions all caused by inherited mutations in genes involving the structure and function of the nerves that serve your feet, legs, hands and arms.
In some cases, these genetic mutations result in damage to the nerve itself. Other mutations damage the myelin sheath, the protective coating that surrounds the nerve. The end result, however, is the same - weaker messages traveling between your extremities and your brain.
That means some of the muscles in one's feet may not receive the brain's signal to contract, so one is more likely to trip and fall. In addition, one's brain may not receive pain messages from the feet, so if one has a blister on the toe, for example, it may get infected without one realizing it.
Pathologic Changes
Neurons, Schwann cells, and fibroblasts work together to create a working nerve. Schwann cells and neurons exchange molecular signals that regulate survival and differentiation. These signals are disrupted in CMT. Demyelinating Schwann cells cause abnormal axon structure and function. They may cause axon degeneration, or they may simply cause axons to malfunction. The myelin sheath allows nerve cells to conduct signals faster. When the myelin sheath is damaged, nerve signals are slower, which can be measured by a common neurological test called electromyography. When the axon is damaged, on the other hand, this results in a reduced compound muscle action potential (CMAP).
Treatment progress
There currently is no effective drug to treat this disease. Moderate rehabilitation training can help maintain joint mobility. After more than 10 years of research, the Wu Stem Cell Medical Center (WSCMC) found that neural stem cells have good therapeutic effects on this disease. Neural stem cells can differentiate into functional neurons and myelin sheath, to repair a part of the damaged neural axon and myelin sheath, which improves the motor function of the patient. At the same time, these kinds of neural stem cells have the normal gene, so their genetic product can make up abnormal products of gene mutation of some patients, which can slow or stop the progress of disease. However, simply implanting stem cells to treat the disease has had no positive effect. Stem cell treatment also needs complicated regulation in vivo, including the cellular localization, differentiation and cellular functional expression in the body.
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