PKU is a genetic metabolic disorder in which the body lacks a liver enzyme (phenylalanine hydroxlase) needed to process phenylalanine, an essential amino acid, into another amino acid (tyrosine) used by the body. Left unconverted, excessive amounts of phenylalanine in the bloodstream are toxic to brain tissue and the central nervous system; if untreated in newborns, PKU can cause brain damage and mental retardation.
There is no drug that can cure PKU. It can only be treated through diet. Because phenlylalanine is a component of proteins, patients must follow a strict low-protein diet, avoiding meat, fish, eggs, poultry, dairy and soy products as well as products containing the artificial sweetener aspartame. “When phenylalanine levels become too high, PKU patients can suffer movement disorders, such as tremors, seizures and hyperactivity,” explains Jeff Sitterle, chief scientist at the Georgia Tech Research Institute (GTRI) and project director for the PKU testing device.
Blood-testing requirements vary depending on the severity of a patient’s condition, but frequent monitoring is especially important for children. The goal is to maintain phenylalanine levels in the blood between 2 and 10 milligrams per deciliter. Pregnant women must also be careful, for if phenylalanine levels get too high, it can affect development of the fetus.
In the United States, there are about 120 centers where PKU monitoring is conducted. That means frequent testing can be costly and inconvenient for patients who must travel long distances to reach a center.