A female newborn delivered at 32 weeks of gestation presented with multiple joint contractures consistent with arthrogryposis multiplex congenita (AMC). The girl died after a four days course of severe respiratory distress. Autopsy revealed slightly hypoplastic and immature lungs with acute necrotizing bronchopneumonia, and marked consecutive hypoxic brain lesions with severe periventricular haemorrhages. The peripheral nerves including the cranial and spinal nerve roots showed a hypomyelination radiculoneuropathy with well preserved axons and a normal content of Schwann cells. In the skeletal muscles of the arms and legs some fascicles of the extensors were replaced by lipomatous tissue. Since myelination of the white matter in the central nervous system was adequate to the age, this case represents an exclusive maturation disorder of the peripheral myelin sheaths that may be considered causal for AMC.