Charcot-Marie-Tooth (CMT)

Case Study A
A 10-year-old boy complained of leg cramps and clumsiness. His motor development was normal. He was in the fifth grade and was performing well academically. At age seven, he had begun to walk on his toes. He had sprained his right ankle twice in the last year and had also complained of hand cramps after long periods of writing. His maternal grandfather had "weak feet" and his maternal uncle had leg braces. His mother had no complaints, except for occasional leg cramps after long walks. Two younger siblings had no neurological complaints.

He appeared healthy, and his gait showed toewalking and, that he was unable to walk on his heels. His heel cords were tight and there was weakness (4/5) of the dorsiflexors of both feet. The legs showed mild atrophy of the anterior tibialis and peroneal muscles. There was no atrophy or weakness of the intrinsic hand muscle. The stretch reflexes were absent in the upper and lower limbs. The plantar responses were flexor. There was decreased pricking sensation distally in stocking distribution. The great auricular nerves were enlarged on both sides, but the left was more visible. When palpated, the ulnar and peroneal nerves were found to be enlarged. He had mild pes cavus deformity.

The patient had a chronic, predominantly motor, hypertrophic polyneuropathy. The most likely diagnosis was chronic inflammatory demyelinating polyneuropathy. The hereditary nature of the disease was confirmed by examining his mother who was mildly obese, could not walk on her heels, and was areflexic. Her nerve conduction velocities (NCV) were 24.7m/s in both median and ulnar nerves without multifocal blocks. The family history suggested an autosomal dominant inheritance pattern.

Molecular tests showed that the CMT1A duplication was present in the individual, his mother, and a younger brother. Motor nerve conduction velocities were performed: the motor NCV of the right peroneal nerve was 14.7m/s; the motor NCV of the left ulnar nerve was 16.9m/s; and the motor NCV of the right median nerve was 21.2m/s. He had motor distal latencies that were proportionately prolonged and absent sensory nerve action potentials. There was no electrophysiological evidence of motor conduction blocks or abnormal temporal dispersion. Lack of conduction blocks argued against chronic inflammatory demyelinating polyneuropathy (CIDP).

Based on the molecular studies and electrophysiological examination, the diagnosis of Charcot-Marie-Tooth type 1A polyneuropathy was made.

Physical therapy to stretch the heel cords and ankle foot orthosis (AFOs) improved his gait.

1. Click here to launch the software with the findings from this case already entered, illustrating that various forms of CMT are by far the leading diagnoses (clicking the "Patient's findings" tab shows the pertinent positives and pertinent negatives used).
2. Click the "Add findings" tab to see a list of useful clinical findings.  Even on the default "Clinical > labs" display, tests for the relevant genes are considered far more useful than getting further clinical or other lab information.  Leading the suggestions is the CMT1A gene (PMP22) test. 
3. Click the PMP22 button to see the link in the yellow box at the bottom of the screen leading to details of how to order the test.