"Cerebral Palsy" in a Patient With Arginase Deficiency.

Inborn errors of metabolism (IEMs) are thought to present in infancy with acute decompensation including feeding intolerance and vomiting, lethargy, and coma. Most practitioners assume that children will be diagnosed in their first months of life. However, certain IEMs present more insidiously, and occasionally children fail to receive newborn screening resulting in delayed diagnoses, as metabolic and genetic disorders are overlooked causes of cognitive and neurologic deficits. Although signs and symptoms may be present but subtle, careful and detailed history taking, particularly of a child's diet and neurologic medical history, in addition to certain physical examination findings may suggest a diagnosis that is later supported by laboratory and radiographic testing. We present the case of an 11-year-old girl who presented with a diagnosis of cerebral palsy, seizure disorder, and concerns of fatigue and increasing seizure frequency. During hospitalization, she was found to have hyperammonemia, and a diagnosis of arginase deficiency was made. More thorough review of her previous records may have raised suspicion for IEM earlier.