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Hereditary neuropathy is an inherited neurological disorder. It affects the peripheral nervous system, which consists of nerves and ganglia — clusters of nerve cells — that lie outside of the brain and spinal cord. These nerves course throughout the limbs and internal organs, connecting them to the central nervous system. There are four major subcategories of hereditary neuropathy: hereditary sensory neuropathy, hereditary motor neuropathy, hereditary motor and sensory neuropathy, and hereditary sensory and autonomic neuropathy.
Symptoms of hereditary neuropathy vary according to type and may include such sensory symptoms as pain, numbness and tingling in the feet and hands, or motor symptoms such as weakness and decreased muscle mass, especially in the lower legs and feet. Hereditary neuropathies that affect the autonomic nervous system can result in sweating disorders, sudden drops in blood pressure on standing, and insensitivity to pain. High arches, hammer toes, thin calf muscles and scoliosis, all of which are associated with hereditary neuropathy, may be present at birth or develop later in life. Genetic testing, nerve biopsies and nerve conductivity tests may be utilized to identify hereditary neuropathies.
Treatment for hereditary neuropathies centers on relieving the most problematic symptoms. In some instances, physical therapy and pain medications may be helpful. Beyond these palliative measures, however, there are no standard treatments for hereditary neuropathy. Severe foot or skeletal deformities may be corrected to varying degrees by orthopedic surgery, and mobility may be improved by bracing, but there is no cure.
The prognosis for people with hereditary neuropathy depends on the type that affects them. Some types are so mild that their symptoms may not even be noticed. In these cases, the disorder can go undiagnosed for years and may never become a serious issue. On the other hand, the more severe types can cause significant difficulties and may result in disabilities.
Charcot-Marie-Tooth disease (CMT), a motor-sensory neuropathy named for the three physicians who first identified it, is the most common type of hereditary neuropathy. Initially, CMT causes weakness and wasting of the muscles of the feet and lower legs. Foot drop or a high-stepped gait that causes tripping and falling may be the result of this condition. Deformities such as high arches or hammertoes are also characteristic of CMT.
The muscle weakness characteristic of CMT is the result of demyelination, which is the destruction of the myelin sheath that protects neurons. Demyelination disrupts nerve signals before they reach the muscle. As CMT progresses, the muscles of the hands may also begin to weaken and atrophy, which can cause the loss of fine motor skills. Rarely, muscles of the diaphragm and respiratory system may be affected, but CMT is not considered fatal, and most patients enjoy a normal life expectancy.