What is PKU?
Phenylketonuria (PKU) is a genetic inborn error of metabolism that is detectable during the first days of life with appropriate blood testing (newborn screening). The absence or deficiency of an enzyme that is responsible for processing the essential amino acid phenylalanine characterizes PKU. With normal enzymatic activity, phenylalanine is converted to another amino acid (tyrosine), which is then utilized by the body. However, when the phenylalanine hydroxylase enzyme is absent or deficient, phenylalanine abnormally accumulates in the blood and is toxic to brain tissue. Without treatment, most infants with PKU develop mental retardation. Those with untreated PKU may also develop additional neurologic symptoms. To prevent mental retardation, treatment consists of a carefully controlled, phe-restricted diet begun during the first days or weeks of life. Most experts suggest that a phe-restricted diet should be lifelong. A carefully maintained diet can prevent mental retardation as well
