Charcot-Marie-Tooth disease type 1

A diagnosis of Charcot-Marie-Tooth disease type 1 (CMT1) can be made based on signs and symptoms and molecular genetic testing. People with symptoms of CMT1 should be evaluated by a neurologist. Evaluation may include a thorough neurological exam, special nerve studies, and consideration of medical and family histories. If CMT is suspected, tests that may be ordered include:

• nerve conduction studies - electrodes are placed on the skin over nerves and produce small electric shocks. This stimulates the nerves and provides quantifiable information for the doctor.
• electromyography (EMG) - involves inserting a needle electrode through the skin to measure the bioelectrical activity of muscles. Specific abnormalities in the readings can be useful in characterizing the distribution and severity of peripheral nerve involvement.

A clinical diagnosis may be considered in individuals with:

• progressive peripheral motor and sensory neuropathy
• slow nerve conduction velocity (NCV)
• palpably enlarged nerves, especially the ulnar nerve at the elbow and the greater auricular nerve running along the side of the neck
• a family history consistent with autosomal dominant inheritance

Genetic testing results can usually confirm a diagnosis. Different genetic testing strategies have been proposed in people with symptoms of CMT1, as several genes are associated with the condition. One testing strategy involves testing a single gene at a time, starting with the gene most commonly responsible, and ending with gene least commonly responsible. An alternative genetic testing strategy is using a multi-gene panel that includes all genes of interest. Molecular genetic testing is needed to distinguish the subtype of CMT1 (type A through F), which is based on the responsible gene and mutation.

The Genetic Testing Registry (GTR) provides information about the genetic tests for CMT1. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

The long-term outlook (prognosis) for people with Charcot-Marie-Tooth disease type 1 (CMT1) varies because the severity of the condition varies. Some people with CMT1 have extremely mild disease that goes unrecognized, while others have considerable weakness and disability.

In general, the condition is slowly progressive (gradual). Affected individuals often experience long periods without obvious deterioration. Most people with CMT1 remain ambulatory throughout life with fewer than 5% becoming wheelchair dependent. Life expectancy for affected individuals is normal.