Salient Features of Histidinemia

SINCE OUR description in 1961, with Dr. A. Hunter, of two children with an inborn error of histidine metabolism, 18 other cases have been reported (Table). Two thirds of the patients are girls. The youngest patient is 1 month of age and the oldest is 13 years. The mental abilities and speech development of the three patients under 1 year of age are difficult to assess accurately. Thirteen of the 17 patients have speech defects. The degree of mental retardation varies greatly from four normal-looking healthy children with definite evidence of the biochemical anomaly to six retarded children with IQs of about 50. The remaining seven have IQs of 65 to 85. The emerging clinical picture, when symptomatology is present, consists of a speech defect, mental retardation of mild to moderate degree, light-colored hair and eyes, and, possibly, growth retardation. Positive results of urinary tests with ferric chloride or Phenistix