Opinion ID: 1839071
Heading Depth: 1
Heading Rank: 3

Heading: What is PKU? [2]

Text: Phenylketonuria (PKU) is a metabolic disease caused by an inherited defect in the enzyme, phenylalanine hydroxylase, which converts phenylalanine to tyrosine. Phenylalanine and tyrosine are important amino acids in body metabolism. For example, tyrosine is important in thyroid function, neurotransmitter function and melanin formation. In a normal person, 95% of the phenylalanine in his diet is converted to tyrosine. As soon as an infant begins to take in protein by mouth, its blood phenylalanine concentration rises. PKU is an inherited, recessive condition, which means that both parents must be carriers of the PKU gene, thus creating a one-fourth chance of producing a PKU child. Approximately 1/10,000 births are PKU in European populations; therefore, 1/2,500 such couples exist, or 1/50 members of the population carry the PKU gene. [3] This is a very rare disorder, and the birth of a PKU child is nearly always unpredictable. There is no way to discover if the parents are carriers of the gene because there are no symptoms or indication of the disease and the children are born healthy. The most effective way to detect the disease is to organize programs that can test every infant shortly after birth. In PKU, phenylalanine accumulates in the blood and body tissues because it cannot be converted to tyrosine. The excess phenylalanine causes severe brain damage resulting in severe mental retardation, and at times seizures, cerebral palsy and microcephaly. In the 1950's, Dr. Robert Guthrie developed a newborn test procedure which detects PKU. The test is a standardized simple method of detecting PKU, and it has been administered on a routine basis at the Mississippi Baptist Medical Center since 1965. Although the state recognized the need for conducting screening tests as early as 1979, the tests were not required until 1985. Cf. MISS. CODE ANN. § 41-21-203 (1972) (physician may provide) with § 41-21-203 (Supp. 1989) (physician shall provide). Untreated PKU persons usually have intelligence quotients between 25-50, and many of these reside in state institutions for the retarded because of associative behavioral problems. Early diagnosis and treatment, consisting merely of a change in the infants' diet can successfully prevent all the clinical manifestation of the disease. Wachbroit, Making the Grade: Testing for Human Genetic Disorders, 16 Hofstra L.Rev. 583, 594 (1988).