PT - JOURNAL ARTICLE AU - A Ponzone AU - O Guardamagna AU - S Ferraris AU - G Bracco AU - A Niederwieser AU - R G Cotton TI - Two mutations of dihydropteridine reductase deficiency. AID - 10.1136/adc.63.2.154 DP - 1988 Feb 01 TA - Archives of Disease in Childhood PG - 154--157 VI - 63 IP - 2 4099 - http://adc.bmj.com/content/63/2/154.short 4100 - http://adc.bmj.com/content/63/2/154.full SO - Arch Dis Child1988 Feb 01; 63 AB - Two patients with dihydropteridine reductase (DHPR) deficiency, in one case due to the absence of any enzyme protein (DHPR- cross reactive material (CRM)-) and in the other case due to the production of a mutant type devoid of catalytic activity (DHPR- CRM+) were examined. This latter form of malignant phenylketonuria, whose relative frequency seems to be higher in the Italian population, possibly has a worse prognosis. The earlier onset and the greater severity of clinical symptoms are associated with a more pronounced hydroxylation defect, as shown by higher degree of neonatal hyperphenylalaninaemia, unresponsiveness to an oral tetrahydrobiopterin load, lower concentrations of neurotransmitter metabolites, and reduced tyrosine production after an oral phenylalanine load.