Complete reversal of moderate/severe brain MRI abnormalities in a patient with classical phenylketonuria

Abnormalities on magnetic resonance imaging (MRI) of the brain are common in older patients with phenylketonuria (PKU; McKusick 261600) (Cleary et al 1994). We, and others, have previously demonstrated that these changes are partially reversible following an improvement in biochemical control (Bick et al 1993; Cleary et al 1995). We now report a patient with classical PKU in whom MRI abnormalities completely resolved following a strict low-phenylalanine (phe) diet.