Phenylketonuria and its Dietary Therapy in Children

Phenylketonuria (PKU) is the most common autosomal recessive disease. Hyperphenylalaninemia is caused by deficiency or inactivity of the phenylalanine hydroxylase in liver. In this disorder phenylalanine in not metabolized to tyrosine. Increased levels of blood phenylalanine causes irreversible brain damage. As infants with PKU do not show any clinical signs in the postnatal period, first stage in treatment is an effective screening and diagnosis. Main treatment of PKU is diet therapy, which should be initiated before the third week of life and monitored by a team formed of a pediatrician, an experienced dietitian, a psychologist, a social worker and a nurse. Phenylalanine-restricted diet should provide enough protein–energy and other nutrients for an optimal growth and brain development and include tyrosine supplement to preserve the phenylalanine plasma concentration in a range of 2 to 6 mg/dl. The exact amount should be prescribed based on age, specific genotype, growth rate and individual need for energy. Successful management of PKU patients should be monitored by growth rate. Duration of diet therapy is controversial; continuing phenylalanine-restricted diet beyond adolescence is recommended.