Histidinemia discovered by urine screening after renal transplantation.

Histidinemia has been discovered by urine screening in a 17-year-old French-Canadian female, who has a single, transplanted cadaver kidney. She has normal intelligence and speech. Activity of L-histidine, ammonia-lyase (histidase) was absent in stratum corneum and other organs. The transplanted kidney handled histidine and its metabolites efficiently. The trait was inherited as an autosomal recessive, with both parents exhibiting deficient histidase activity. The patient is ently chimerical for histidase activity. The host cells contain no activity; the implanted kidney presumably contains the normal but ineffective amount of histidase activity. Homozygotes with certain inborn errors of metabolism might benefit in the future from "transplant chimerism" if the appropriate organ containing the missing enzyme were implanted.