PKU, which stands for Phenylketonuria, is an inherited metabolic disease, also called an inborn error of metabolism. It leads to mental retardation and other developmental disabilities if untreated in infancy. With an inborn error of metabolism, the body is unable to produce proteins or enzymes needed to convert certain toxic chemicals into nontoxic products, or to transport substances from one place to another. PKU is inherited as a single-gene disorder, which is caused by a mutant or abnormal gene. In order to inherit PKU both parents must be PKU carriers. When this occurs, there is a one in four chance of their child being affected by PKU. Boys and girls are equally at risk of inheriting this disorder. One in every 12,000 to 15,000 babies is born with PKU.
In people with PKU, the amino acid called phenylalanine accumulates. As phenylalanine builds up in the bloodstream, it causes brain damage. Infants with untreated PKU appear to develop typically for the first few months of life, but by twelve months of age most babies will have a significant developmental delay and will be diagnosed with mental retardation by school age.
Today all states routinely screen newborns for PKU. To test the newborn a few drops of blood are collected from a heel prick. The blood sample is then tested in a state laboratory for abnormal amounts of phenylalanine. The normal level is less than 2 milligrams. Newborns with 20 milligrams or higher are considered likely to have PKU. Newborns with 6 or 8 milligrams should be treated with a modified phenylalanine restricted diet.
PKU’s symptoms can often be treated successfully through a diet that consists of foods that have a restricted phenylalanine content. Babies are given a special formula that contains very low levels of phenylalanine. Children can gradually progress eating certain vegetables, fruits and other foods that are low in phenylalanine. People with PKU should stay on a restricted diet indefinitely in order to maintain a safe level of phenylalanine.
If you would like more information on PKU please contact National PKU News at 202-525-8140, or visit them online at www.pkunews.org, or The Children’s PKU Network at 619-233-3202, or online at www.pkunetwork.org.
Phone code: 1722