A case of congenital diaphragmatic paralysis is reported in an infant who died because of respiratory failure at the age of 5 weeks. The histologic findings show a dystrophy-like muscle pathology restricted to the diaphragm with a normal somatic peripheral musculature and normal phrenic nervous structures. The previous death of a male sibling because of diaphragmatic eventration suggests that this case of diaphragmatic paralysis could have been a consequence of a partial and random hypoplasia of muscle fibers, mimicking an isolated muscle dystrophy of the diaphragm.