n.
or phenylpyruvic oligophrenia
Inability to normally metabolize phenylalanine , the accumulation of which interferes with normal childhood development.
Central nervous system effects include mental retardation and seizures (see epilepsy ), with behavioral signs seen at four to six months of age. Abnormal metabolism also leads to low melanin levels, with light hair, eye, and skin colour. Tests detect this recessive genetic disorder (see congenital disorder ; recessiveness ) in two-thirds of the 1 in 10,000 newborns born with high levels of phenylalanine. Keeping phenylalanine out of the diet (by total avoidance of meat, dairy, and high-protein foods and aspartame ) until adolescence permits normal development. Protein is supplied in a phenylalanine-free formula. Pregnant women with PKU must resume the diet to prevent severe damage to the unborn child.