Phenylketonuria

Phenylketonuria (PKU) is an inherited metabolic disorder caused by a deficiency of the enzyme phenylalanine hydroxylase, which normally converts the amino acid phenylalanine into tyrosine. Without this enzyme, phenylalanine accumulates to toxic levels in the blood and cerebrospinal fluid, causing intellectual disability, behavioral problems, and neurological complications if left untreated. Fortunately, PKU is one of the first conditions routinely screened for in newborns across the U.S. and many other developed countries. When identified early and managed properly through a specialized low-phenylalanine diet, individuals with PKU can have normal intellectual development and a normal lifespan. However, maintaining the strict dietary requirements throughout childhood and often into adulthood is essential, as uncontrolled phenylalanine levels can develop at any age.