Unexpected white matter changes in an early treated PKU case and improvement after dietary treatment.

We report a case of classic phenylketonuria (PKU) treated by dietary restriction until the age of 5 years. At the age of 18 years, she developed anxious-depressive symptoms and deterioration of school performance. Neurophysiological investigations showed changes in VEPs and BAEPs and brain MRI showed white matter abnormalities. The return to a diet low in phenylalanine reduced psychiatric disturbances and reversed neurophysiological and MRI changes. Our data confirm previous observations of white matter involvement in PKU and the utility of lifelong dietary therapy to prevent neurological and/or psychiatric deterioration.