Phenylketonuria neonatal screening

During the past 20 years, neonatal screening programs using the Guthrie test for inborn errors of metabolism such as phenylketonuria have become more widely used. The characteristics of diseases in which mass screening is... 

Phenylketonuria [PKU (261600)1 is an autosomal recessive disease that causes severe mental retardation if it is undetected. Two normal parents are told by their state neonatal screening program that their third child has PKU. Assuming that the initial screening is accurate, what is the risk that their first child is a carrier for PKU ... 

As part of a standard neonatal screen, an infant is diagnosed with a loss of function genetic defect in the enzyme phenylalanine hydroxylase. Defects in this enzyme can result in a condition known as phenylketonuria (PKU), which results from the toxic effects of phenylalanine derived phenylketones. Fortunately, this condition can be managed by regulating the amount of phenylalanine provided in the diet. Which of the following nonessential amino acids will need to be supplied in the diet of this infant ... 

Neonatal screening can identify some disorders, such as phenylketonuria, in the newborn baby in the first days of life (pp. 144-145). 

Beasley MG, CosteUo PM, Smith I. Outcome of treatment in young adults with phenylketonuria detected by routine neonatal screening between 1964 and 1971. Q J Med 1994 87 155-160. 

Zhan J-Y, Qin Y-F, Zhao Z-Y. Neonatal screening for congenital hypothyroidism and phenylketonuria in China. World J Pediatr. 2009 5(2) 136-9. 

The concentration of phenylalanine in the blood of neonates is used to screen for phenylketonuria (PKU). Explain the biochemical basis for the correlation of elevated blood phenylalanine concentration and PKU. Explain why restriction of dietary phenylalanine is critically important for youngsters with PKU. 

Sometimes a test for more than one protein is needed and mass spectrometry is the method of choice for that purpose. A good example for this would be the use of tandem mass spectrometry to screen neonates for metabolic disorders such as amino acidemias (e.g., phenylketonuria—PKU), organic acidemias (e.g., propionic acidemia—PPA), and fatty acid oxidation disorders (e.g.. Medium-chain acyl-CoA Dehydrogenase deficiency—MCAD) [9]. Although the price of this capital equipment could be high, costs of using it as a sensor is quite low (usually < U.S. 50.00 to screen for more than 20 metabolic disorders), and many states in the United States provide the service to newborns during the first week of life. 

PKU is caused by deficiency of phenylalanine hydroxylase that converts phenylalanine to tyrosine. Routine screening for phenylketonuria is undertaken in neonates. 

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