A boy, aged 2 years, presenting at birth as a case of rhabdomyolysis and later shown to have an X-linked recessive dystrophy, is reported from the Section of Child Neurology, St. Christopher’s Hospital for Children, Philadelphia, PA, and the Child Neurology A.I. Dupont Institute, Wilmington, DE. Palpation of upper and lower extremities on newborn examination revealed stiff, indurated large muscle groups. The birth was a cephalic presentation without forceps. The CK at 2 days of age was 156,000 IU/1, and a benzidene dipstick for heme and myoglobinuria was negative at 4 days. Repeat CK determinations at 6 days and between 5 weeks and 14 months were approx. 12,000 and 6000-9000 IU/1, respectively. Percutaneous needle biopsy of the quadriceps at 1 year demonstrated many degenerating fibers, marked variation of fiber size, and increase in endomysial and perimysial connective tissue and fat. DNA analysis showed a partial X chromosome deletion adjacent to the Duchenne/Becker locus. On clinical examination the infant was developmentally delayed at 11 months and had speech delay, proximal lower extremity weakness, and calf pseudohypertrophy at 24 months. 
COMMENT. Rhabdomyolysis is an acute muscle necrosis usually accompanied by myoglobinuria which may complicate muscular dystrophy in association with malignant hyperthermia or anesthetic induced cardiac arrest. This patient had neither myoglobinuria nor hyperthermia. A neonatal presentation of Duchenne muscular dystrophy is exceptional, signs usually appearing when the patient becomes ambulant.