Auditory and visual evoked potentials in a 17-year-old boy with undiagnosed classical phenylketonuria

A mentally retarded 17-year-old boy with undiagnosed classical phenylketonuria (PKU) is reported. The mental retardation of an untreated patient with PKU can be studied by electrophysiological investigations, such as auditory and visual evoked potentials, which are also useful to control the course of the disease under a low-phenylalanine diet. In the present case, we only found mild abnormalities of auditory evoked potentials. Visual evoked potentials did not show significant abnormalities, although further evaluations are requested. We point out the relationship between the severity of neurological dysfunction and electrophysiological findings in untreated PKU patients.