Positive effect of a late introduced modified diet in an 8-year-old pku child

A modified low phenylalanine diet was instituted in an 8-year-old PKU boy earlier untreated and mentally retarded. The boy was treated during a ten year observation period. A marked progress in mental capacity and in IQ scoring was seen. The difficulties in objective evaluation of the benefit of late introduced treatment with a diet low in phenylalanine is discussed.