Neurological disturbance in a phenylketonic child after discontinuation of dietary treatment.

Signs of moderately severe spastic diplegia appeared in 14-year-old late-treated phenylketonuric boy 13 months after dietary restrictions were lifted. The literature contains reports of untreated phenylketonuric patients developing demyelinating conditions in later childhood. The possible implications of relaxing the diet in early- and late-treated cases of phenylketonuria are discussed.