Case records of the Massachusetts General Hospital. Case 35-2006. A newborn boy with hypotonia.

A 2-day-old boy was admitted to the special care nursery of this hospital because of hypotonia. He was delivered at another hospital to a 40-year-old mother (gravida 2, para 2) at 38 weeks and 6 days of gestation by a scheduled cesarean section, which was the mother’s second. The pregnancy was uneventful, and tests for rapid plasma reagin, hepatitis B surface antigen, and group B streptococcus were negative in the mother. Her blood type was A positive, with negative results on antibody screening, and she was immune to rubella. Fetal movements during the pregnancy were normal. The delivery was uncomplicated, but the infant initially had a weak cry and decreased tone in his arms; the cry improved with the administration of blow-by oxygen. The Apgar scores were 8 at 1 minute and 9 at 5 minutes. The birth weight was 3815 g. During the first day, decreased muscle tone in the arms and legs and a highpitched cry were noted. Six hours after birth, the infant had an episode of tachypnea, with an oxygen saturation of 87%; oxygen was administered, and the patient was weaned from supplemental oxygen and breathing ambient air by day 2 of life. The complete blood count and levels of serum electrolytes, calcium, phosphorus, and magnesium were normal. The total bilirubin level was 7.2 mg per deciliter (123 μmol per liter). The baby was initially breast-fed without difficulty but fed poorly on day 2 of life. The hypotonia worsened, and the high-pitched cry persisted. He was transferred to this hospital. The patient’s 14-year-old half-sister was well. The infant’s father reported being told that he did not sit up until he was 10 months old and was spoon-fed as an infant because he was a “lazy feeder”; he was unable to walk or hold anything until he reached 21 2 years of age. No explanation had been given for the father’s weakness. His subsequent development was normal, and he was functioning normally at 35 years of age. The baby’s mother had no medical problems. There was no other family history of neurologic or muscular diseases. On admission, the patient’s weight was 3440 g, the length 50.8 cm, and the head circumference 36 cm. He was not in acute distress. The blood pressure was 85/49 mm Hg, and the pulse 130 beats per minute; the respirations were 32 breaths per Case 35-2006: A Newborn Boy with Hypotonia