Histidinuria: defective transport of histidine.

A-7-year-old boy was found to have histidinuria without histidinemia. Low concentrations of histidine in plasma were consistent with impaired intestinal and renal tubular absorption of histidine. The patient was developmentally delayed and had some minor anomalies. Only 4 other patients in 3 families have been reported. Each had abnormality of the central nervous system. All were male.