phenylketonuria

phenylketonuria (PKU), inherited metabolic disorder caused by a deficiency in a specific enzyme (phenylalanine hydroxylase). The absence of this enzyme, a recessive trait, prevents the body from making use of phenylalanine, one of the amino acids in most protein-rich foods, and almost always leads to mental retardation and schizoid changes when phenylalanine levels rise; convulsions also commonly occur. Early diagnosis and treatment, which includes a carefully regulated low-phenylalanine diet begun during the first few weeks of life, may prevent serious mental deficiency. Positive improvement has been seen even when therapy is started in well-established cases. In 2007 the FDA approved the use of sapropterin dihydrochloride as a treatment. The drug can boost the ability of persons with low levels of phenylalanine hydroxylase to break down phenylalanine but will not help those who lack the enzyme. Most states have made the PKU blood or urine test mandatory for all newborn infants.

phenylketonuria (PKU) (fee-nyl-kee-tŏn-yoor-iă) n. an inherited defect of protein metabolism (see inborn error of metabolism) causing an excess of the amino acid phenylalanine in the blood, which damages the nervous system and leads to severe mental retardation. The gene responsible for phenylketonuria is recessive, so that a child is affected only if both parents are carriers of the defective gene.
www.pku.com This US website includes the diagnosis of PKU by the Guthrie test

phenylketonuria A genetic disorder in which there is disordered metabolism of the amino acid phenylalanine, leading to severe mental retardation of affected children. The disease is caused by the absence or deficiency of the enzyme phenylalanine hydroxylase, which results in the accumulation of phenylalanine in all body fluids. There are also high levels of the ketone phenylpyruvate in the urine, hence the name of the disease. The disease occurs in individuals who are homozygous for the defective recessive allele; both parents of such individuals are thus heterozygous carriers of the allele. The advent of gene probes has greatly aided accurate diagnosis, of both phenylketonurics and carriers.