Perinatal pathology casebook.

Citrullinemia, a rare inborn error of metabolism, is characterized by a deficiency of argininosuccinic acid synthetase that results in large increases in plasma ammonia, citrulline, and glutamine, with normal acid-base balance. The neurologic symptoms vary from poor feeding, vomiting, and irritability to hypotonia, apnea, and death. The most common pathologic findings at autopsy are cerebral edema and focal neuronal necrosis. We describe a case of fulminant citrullinemia in an infant in whom the major pathologic findings included diffuse cerebral edema and a lack of overt metabolic derangement characteristic of neonates with a urea cycle defect. Our case differs from the classic presentation of citrullinemia in that subarachnoid hemorrhage was identified early in the clinical course. We report the first observation of subarachnoid hemorrhage in an infant with a urea cycle defect.