[A new form of the Lesch-Nyhan syndrome. A study of hypoxanthine-guanine-phosphoribosyl-transferase in fibroblasts. The in vitro and in vivo effect of adenine on enzyme activity].

A new, clinically and biochemically atypical case of Lesch-Nyhan syndrome is presented. There is mild neurological involvement, the APRTase activity is normal, despite a raised PRPP concentration and HGPRTase activity is low. The optimal pH and temperature of fibroblast HGPRTase activity differ markedly from control values. The Km for hypoxanthine and PRPP are minimally changed. Erythrocyte HGPRTase activity does not vary following adenine ingestion in either the adult patient or the control. Fibroblast HGPRTase activity is not affected by the addition of adenine to cultures of fibroblasts. However, in the child suffering from classical Lesch-Nyhan syndrome, erythrocyte HGPRTase activity decreases following adenine ingestion.