Abstract

A 6-month-old child with a history of recurrent infections, convulsions, and retarded development had biochemical findings which were typical of histidinaemia. The enzyme histidase has been shown to be absent from the skin of the patient. The results of histidine-loading experiments in the parents of the child suggest that they may both metabolise this amino-acid abnormally. A simple method of estimating histidine in plasma and urine is described.