HEREDITARY TYROSINEMIA TYPE-I - SELF-INDUCED CORRECTION OF THE FUMARYLACETOACETASE DEFECT

Two Norwegian patients with chronic tyrosinemia type I showed > 50% re sidual fumarylacetoacetase activity in liver samples obtained during l iver transplantation. The enzyme characteristics of both patients were comparable with those of a normal control. Immunohistochemistry on li ver sections from these patients and from three other Norwegian tyrosi nemia patients revealed a mosaicism of fumarylacetoacetase immunoreact ivity corresponding completely or partly to some of the regenerating n odules. This appearance of enzyme protein is presumably induced by the disease process. The mechanism involved remains unclear and could be caused by a genetic alteration, regained translation of messenger RNA, or to enhanced stability of an abnormal enzyme.