Charcot-Marie-Tooth disease

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at October 28, 2016
StartDiseasesCharcot-Marie-Tooth disease

In 1886, three physicians identified an inherited progressive muscular atrophy disease. Charcot-Marie-Tooth disease, or CMT is a genetic disorder and was named after its discoverers, Englishman Dr. Howard Henry Tooth and Frenchmen, Dr. Pierre Marie and Dr. Jean-Martin Charcot.

Contents

Definition & Facts

Some physicians refer to Charcot-Marie-Tooth disease as hereditary motor and sensory neuropathy. Today, CMT afflicts about one person in every 2,500 in the United States. It results in a gradual deterioration of some nerves, but does not usually cause death or shorten the lifespan of patients.

Medical scientists recently identified several different subtypes of CMT and more than 70 different specific varieties of CMT. Recent advances in the study of genetics have produced a growing body of information about this condition, allowing physicians to connect the development of subtypes of CMT with very specific mutations.

Symptoms & Complaints

The first signs of CMT usually occur in a patient as a teenager or a young adult though some individuals with this condition don't display any symptoms until middle age. The condition potentially afflicts people from every racial and ethnic group.

Since many different varieties of CMT exist, symptoms vary widely from case to case. This hereditary condition usually reduces the ability of nerves to control voluntary and sensory functions. A patient with a type of CMT may notice symptoms developing in the lower extremities first, and then progressing to the arms.

Frequently, CMT patients experience weakness in leg muscles and weakness in feet muscles; due to muscle weakness patients may display hammer toes that turn inwards, high feet arches and, sometimes, skinny calves. They may develop unusual gaits caused by weakened leg muscles.

They also may eventually experience difficulty performing activities that require fine motor skills, such as needlepoint or precision tooling. Some people experience pain as a result of this condition, although the degree of symptoms varies widely from one person to another. Certain patients with advanced cases of peripheral nerve atrophy won't detect sensory information, such as pain, cold or heat as quickly as previously.

Patients with severe cases of CMT may require knee braces or other support to assist them in maintaining full mobility. Some CMT patients eventually experience orthopedic pain resulting over the course of years from increased weakness in certain muscle groups. Muscle weaknesses may contributes to other problems, such as toe deformities or spinal malformations.

Causes

Generally, CMT produces inherited abnormalities that damage the production of proteins involved in maintaining smoothly functioning peripheral nerves. The most widespread types of CMT pass directly from one generation to another. However, sometimes spontaneous mutations cause the condition as well. Symptoms begin appearing as the peripheral nerves gradually lose function and deteriorate over the course of time.

Different versions of CMT arise from different types of gene mutations. For instance, a rare version of CMT called Dejerine-Sottas disease begins at an early age, and physicians have identified at least two specific genetic mutations that may cause this particular condition.

Diagnosis & Tests

Patients who display symptoms of this disease usually visit a neurologist, a physician who specializes in diseases involved nerves and muscles. This consultation typically involves:

If a physician suspects the presence of CMT, the next diagnostic step usually involves the performance of tests on muscles to check nerve conductivity. Individual muscles may be checked using an electromyography machine called an EMG. It indicates the responsiveness of muscles to bioelectrical activity. This type of testing may allow a physician to determine whether peripheral nerve atrophy appears to have created symptoms in the muscles. MRIs may prove helpful in diagnosing some patients, also.

Genetic testing will diagnose some subtypes of Charcot-Marie-Tooth disease, but not all subtypes. A definitive diagnosis may require a peripheral nerve biopsy. This kind of biopsy involves a neurologist removing a small portion of peripheral nerve for close examination to determine whether the nerve shows signs of degeneration.

Treatment & Therapy

No effective treatment prevents the development of CMT at this time, but patients with the condition may benefit from several helpful measures designed to alleviate symptoms. Some of these steps include:

Since symptoms of this condition sometimes vary widely between one patient and another, not all treatments fit every patient. For example, one person with CMT may experience only mild muscle weakness later in life, while another may develop severe peripheral nerve deterioration during infancy. Patients sometimes benefit from the use of orthotic devices like walkers, thumb splints, and leg braces depending on the individual symptoms they display.

Prevention & Prophylaxis

At this time, no one has discovered a way to prevent the development of CMT. Perhaps in the near future, gene therapy will offer some assistance. Medical researchers have experimented with the use of nutrients as a way to possibly slow the development of this muscle-wasting condition.

For instance, the administration of vitamin C may slow down the development of one widespread version of CMT called "CMT1A". Another study seeks to determine whether curcumin may assist animals afflicted with a version of CMT called "CMT1B".

Ongoing research is also investigating therapies that seek to reverse the processes of muscle wasting and nerve deterioration. Genetic testing and counseling have become available for some types of CMT. This testing may assist parents who have a high risk of transmitting CMT to their offspring. One promising recent line of research that may benefit some CMT patients in the future involves reducing myelin synthesis.