Young infants with PMP22 duplication can have minor nerve conduction study abnormalities.

Charcot-Marie-Tooth disease type 1A (CMT1A) is related to PMP22 gene duplication. It is characterized at electrodiagnostic testing (EDX) by diffuse homogeneous signs of demyelination, such as velocity slowing and prolonged distal latencies. These abnormalities are less pronounced in infants under two years old, and the possibility of normal nerve conduction studies (NCS) in infants with CMT1A under one year of age has been questioned. We report three infants who displayed normal or almost normal NCS. EDX abnormalities in CMT1A patients may therefore appear late during development. This may affect early EDX diagnosis in infants and should be considered for upcoming clinical trials.