Index of Suspicion In the Nursery

Abstract

A 9-day-old Hispanic boy presents to the emergency department with seizures and apnea. The seizure lasts for about 3 minutes and is characterized by stiffening of the body and laryngospasm. Laboratory evaluation reveals a serum calcium concentration of 6 mg/dL (1.5 mmol/L). Hypocalcemic tetany resolves after administration of intravenous calcium. The infant also has fever of 100.4°F (37.7°C). The infant was born at term, and his birthweight was 3.2 kg. He is the fifth child born of nonconsanguineous parentage. The antenatal period was uneventful. Because the family does not have insurance, the mother had not taken prenatal vitamins and supplements. The baby has been fed with human milk and formula. On physical examination upon admission to the hospital, his temperature is 99°F (36.9°C), pulse is 186 beats/min, respiratory rate is 54 breaths/min, blood pressure is 97/64 mm Hg, and weight is 3.83 kg. He has no dysmorphic features and is normocephalic, with an open and flat anterior fontanelle without craniotabes. No cataracts or Chvostek sign are present. Cardiovascular examination reveals a regular heart rate and rhythm, with no murmurs. The lungs are clear to auscultation bilaterally, and there is no hepatosplenomegaly. Neurologic findings are normal. Laboratory evaluation reveals: sodium, 136 mEq/L (136 mmol/L); potassium, 5.2 mEq/L (5.2 mmol/L); chloride, 101 mEq/L (101 mmol/L); bicarbonate, 26 mEq/L (26 mmol/L); blood urea nitrogen, 10 mg/dL (3.57 mmol/L); creatinine, 0.3 mg/dL (26.5 mcmol/L); glucose, 109 mg/dL (6.1 mmol/L); calcium, 6.6 mg/dL (1.65 mmol/L); phosphorous, 10.5 mg/dL (3.4 mmol/L); albumin, 3.0 g/dL (30 g/L); and magnesium, 2 mg/dL (0.82 mmol/L). The white blood cell count and differential count are normal. Findings on cerebrospinal fluid evaluation are normal. However, the 25-hydroxyvitamin D concentration is less than 7 ng/mL (17.5 nmol/L) (normal, 10 to 68 ng/mL [25 to 169.7 nmol/L]), the 1,25-dihydroxyvitamin D concentration is 45 …