Review Question - QID 4608

Charcot-Marie-Tooth disease (CMT, also known as hereditary motor and sensory neuropathy/HMSN/or peroneal muscular atrophy) comprises a group of disorders caused by a mutation in the genes that affect the normal function of peripheral nerves. CMT is due to a mutation of PMP22 located at chromosome 17p12 and leads to symmetrical, predominantly distal limb-muscle wasting, weakness, and sensory loss, especially in the lower extremities.

The initial presentation is highlighted by a weakened tibialis anterior and peroneus brevis that is overpowered by a stronger peroneus longus/posterior tibialis, resulting in a plantar flexed first metatarsus and pronated forefoot. Hindfoot varus deformity develops secondarily. As the deformities become more fixed, an equinus contracture will often develop as well.

Illustrations A and B are radiographs demonstrating the significant pes cavus associated with Charcot-Marie-Tooth disease.

Incorrect Answers:
Answer 1&2: Peroneus longus and tibialis posterior is relatively stronger in CMT
Answer 3: Peroneus brevis is weakened in CMT
Answer 4: There is no known effect of the peroneus tertius in the pathophysiolgy of CMT