Cranial MR in phenylketonuria.

Phenylketonuria (PKU) is an autosomal recessive disease in which defects in phenylalanine metabolism result in hyperphenylalaninemia. Untreated patients generally have poor motor function and are profoundly retarded. We report a patient with PKU whose cranial magnetic resonance abnormalities correlate with known histopathologic changes. The ability to image the pathologic changes in PKU may have important implications regarding treatment and prognosis of these patients.