Phenylketonuria (PKU). Biopterin dependent PKU. DHPR (dihydropterin reductase) deficiency.
Incidence
Approxim 70 cases reported.
Clinical Characteristics
Almost always very severe with early onset progressive encephalopathy, with seizures, myoclonus, respirat. & cardiac difficulties and rigidity. The clinical characteristics are: progressive mental and physical retadation, hypotonia/hypertonia, swallowing difficulties, hypersalivation, chorea/athetosis, temperature instability. There is also basal ganglia calcification. The hyperphenylalaninemia and the excreted related org acids are more pronounced than PTS deficiency PKU. It is a bad disease with extrapyramidal symptoms.
Precipitants
none
Provocation Tests
The administration of 20 mg/kg/day BH4 will reduce blood phenylalanine but will increase urine biopterin.
Diagnostic Procedures
Ferric chloride gives emerald green transient color. Urine pterin determination. Urine pterins are abnormal. Large amounts of biopterins EB-RBC. Enzyme activity in liver biopsy.