Case #4 - A Child With Painless Wounds

Review of Diagnosis

Q: What are the symptoms of Charcot-Marie-Tooth disease?

The neuropathy of CMT affects both motor and sensory nerves. Typical features includes weakness of the foot and lower leg muscles, which may result in foot drop, and a high-stepped gait associated with frequent tripping or falls. Foot deformities, such as high arches and hammertoes, are also characteristic of the disease due to weakness of the small muscles in the feet. In addition, the lower legs may take on an "inverted champagne bottle" appearance due to the loss of muscle bulk. Later in the disease, weakness and muscle atrophy may occur in the hands, resulting in difficulty with fine motor skills.

Although sensory nerves are also involved, patients rarely notice significant numbness or pain, as was the case for the patient presented here.

Onset of symptoms is most often in adolescence or early adulthood. However, presentation may be delayed until mid-adulthood. Progression of symptoms is very gradual. CMT is not fatal, and people with most forms of CMT have a normal life expectancy.^[4,5,6]

Q: What are the types of Charcot-Marie-Tooth disease?

The 2 most common forms of CMT or HMSN are CMT I and CMT II. CMTI, which presents earlier in life, is seen on pathologic examination as segmental demyelination with remyelination of the peripheral nerves. (CMT II, the form with typically later onset, is characterized by chronic partial denervation with axonopathy. Both forms produce the same classic symptoms.^[5,6]

Q: What causes Charcot-Marie-Tooth disease?

CMT is caused by mutations in genes that produce proteins involved in the structure and function of either the peripheral nerve axon or the myelin sheath. Although different proteins are abnormal in different forms of CMT disease, all of the mutations affect the normal function of the peripheral nerves, causing slow degeneration. The degeneration of motor nerves results in muscle weakness and atrophy in the extremities (arms, legs, hands, or feet), and the degeneration of sensory nerves results in a reduced ability for proprioceptive sensations.

Some forms of CMT are inherited in an autosomal dominant fashion, whereas other forms of CMT are inherited in an autosomal recessive fashion or X-linked basis.^[7,8]

Q: How is the diagnosis of CMT disease made?

A muscle or nerve biopsy may confirm the diagnosis. Nerve conduction velocity (NCV) tests are often performed to distinguish the axonal form from the demyelinating (HMSN I or II) forms of the disorder. In cases of CMT I, NCVs are usually lower than 38 milliseconds in upper limb nerves, and segmental demyelination and remyelination with onion bulb formations are seen on nerve biopsies. In patients with CMT II, NCVs are greater than 38 milliseconds and biopsies mainly show a loss of myelinated axons.^[4]

Genetic testing is available for most forms of the disease. Type I is most commonly mapped to the short arm of chromosome 17, although a few pedigrees with this phenotype are linked to the long arm of chromosome 1. Type II can be inherited in an autosomal dominant (linked to the short arm of chromosome 1) or autosomal recessive (long arm of chromosome 8) fashion.^[1]

Q: What are the therapeutic approaches for managing CMT disease?

There is no known cure for CMT disease. Treatment is aimed at maximizing the patient's independence. Orthopaedic surgery or equipment (such as braces or orthopaedic shoes) may maximize the patient's ability to walk.

Vocational counseling, occupational therapy, or physical therapy may be appropriate for some people to help maintain muscle strength and maximize independent functioning. Providing a molecular diagnosis could be valuable for patients who desire genetic counseling or family planning.^[4]

Medscape Pediatrics. 2003;5(1) © 2003 Medscape

Cite this: Case #4 - A Child With Painless Wounds - Medscape - Mar 18, 2003.