Urocanic Aciduria: A Defect in the Urocanase Activity in the Liver of a Mentally Retarded

Abstract

A new entity of inborn error of histidine metabolism was described. This was characterized by 1) urocanic aciduria, which was exaggerated after an oral dose of L-histidine, 2) a delayed clearance curve of serum histidine levels after an oral dose of L-histidine, 3) urinary excretion of no detectable amounts of formiminoglutamic acid after an oral load with L-histidine or after an intravenous injection of urocanate, 4) a marked decrease in the urocanase activity of the liver, and 5) mental retardation of probably early onset.