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Phenylketonuria and its Dietary Therapy in Children
Farhud, Daryosh & Shalileh, Maryam
Abstract
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.
Keywords
Phenylketonuria; Phenylalanine; Diet; Hyperphenylalaninemia; Phenylalanine hydroxilase
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