Congenital hypomyelinating neuropathy: a reversible case

A boy was born at 39 weeks gestation with severe weakness and hypotonia, fractured femurs, poor suck and swallow, and absent deep tendon reflexes. Electrodiagnostic studies revealed marked slowing of motor nerve conduction velocities and normal muscle electrical activity with no evidence of acute denervation. Muscle biopsy showed mild type 2 fiber predominance, and sural nerve biopsy revealed large axons without myelin, and axons with insufficient amount of myelin for their diameter. There was no evidence of inflammation or demyelination. Gradual clinical improvement in tone and strength occurred in a cephalocaudal direction. By 4 months, motor nerve conduction velocities and clinical examination were normal apart from absent deep tendon reflexes. On review at 19 months, motor development and neurological examination were completely normal. Pathogenesis of this reversible pathologically documented case of congenital hypomyelinating neuropathy is unclear. No evidence was found for an inflammatory, toxic, metabolic, or demyelinating cause. Abnormal expression of a developmental gene, as in reversible cytochrome oxidase deficiency, may be a cause of this neuropathy.