PKU: Phenylketonuria

Phenylketonuria

   Phenylketonuria or PKU is when the body can’t process an amino acid phenylalanine or Phe. High levels of Phe are found in most proteins. Their bodies do not have the enzyme, phenylalanine hydroxylase (PAH), which converts phenylalanine into a different amino acid into tyrosine. Failure to convert the amino acid results in the buildup of phenylalanine (Phe) and too much Phe becomes toxic to the central nervous system. The degree of Phe in each person is different; therefore the result of a toxic nervous system varies with each patient. Some signs of untreated PKU in infancy are; mental retardation, behavior problems, hyperactivity, irritability, restlessness, seizures, eczema, fair hair and skin, and a musty or mousy body odor (www.newbornscreening.info). A newborn screening can indicate the child may have PKU. It is not definitive until a series of tests confirm the child has PKU. If a newborn has PKU the development of the child gives the impression of normal development. The result of PKU starts to show around six months of age. If immediate treatment of PKU occurs the effects may be prevented and in some cases lessoned or reversed. The main treatment of PKU is a special diet made up of low Phe foods, special medical foods and medicinal formula. Some foods to avoid are; eggs, fish, milk, all dairy products, nuts, regular flour, meat, poultry, regular formula, peanut butter and dried beans (www.pkunews.org, www.newbornscreening.info). Also aspartame should be avoided as it contains high levels of Phe and raises the blood levels of Phe rather quickly (www.newbornscreening.info). This diet should be followed for life and those, adolescence or adults, who do not stick to the diet with high Phe levels may have the following symptoms; irritability, trouble paying attention, eczema, slow thinking, problems making good decisions, tremors and bone loss (osteopenia) (www.newbornscreening.info). If this occurs then the diet should be resumed.

  Children with PKU that has been treated immediately after birth and maintained low Phe levels in the blood most likely will develop normally in growth and intelligence. Some children will have problems in school, even when treated right away, while those who were treated several weeks after birth may have learning disabilities and/or delays. To keep track of Phe levels routine blood tests are taken to measure the Phe. If the levels are not balanced then the diet is adjusted to reflect the change.

References

Schuett, Virginia. “What is PKU?” National PKU News. National PKU News. February 2008. Web. 22 May 2010.

“About PKU.” PKU- Phenylketonuria. BioMarin Pharmaceutical Inc. n.d. Web. 22 May 2010.
“Amino Acid Disorders.” Newborn Screening Info. STAR-G. 16 December 2007. Web. 22 May 2010.