Tetrahydrobiopterin therapy of atypical phenylketonuria due to defective dihydrobiopterin biosynthesis.
A patient with atypical phenylketonuria (defective BH2 synthesis), detected at age 6 months because of severe muscle hypotonia and serum phenylalanine of 20 mg/100 ml, had normal activities of phenylalanine-4-hydroxylase and DHPR in liver biopsy, but only 2% activity in the phenylalanine-4-hyroxylase in vivo test using deuterated phenylalanine. After IV administration of 2.5 mg/kg chemically pure tetrahydrobiopterin bishydrochloride (BH4 . 2HCl), serum phenylalanine decreased from 20.4 to 2.1 mg/100 ml within 3 hours. Administration of 25 mg BH4 . HCl and 100 mg ascorbic acid through a gastric tube decrease; serum phenylalanine from 13.7 to less than 1.6 mg/100 ml within 3 hours and it remained less than 2 mg/100 ml for 2 days.
D001708:Biopterins / Q000031:analogs & derivatives / Q000172:deficiency / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007223:Infant; D010649:Phenylalanine / Q000097:blood; D010661:Phenylketonurias / Q000188:drug therapy* / Q000209:etiology; D011621:Pteridines / Q000627:therapeutic use*
D011621:Pteridines; D001708:Biopterins; D010649:Phenylalanine; C017226:7,8-dihydrobiopterin; C003402:sapropterin