What are the symptoms of phenylketonuria?

Phenylketonuria (fen-ul-key-toe-NU-ree-uh), also called PKU, is a rare inherited disorder that causes an amino acid called phenylalanine to build up in the body. PKU is caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine. read more

The severe signs and symptoms of PKU are rare in the United States, as early screening allows treatment to begin soon after birth. Early diagnosis and treatment can help relieve symptoms of PKU and prevent brain damage. read more

Children with untreated PKU appear normal at birth. But by age 3 to 6 months, they begin to lose interest in their surroundings. By age 1 year, children are developmentally delayed and their skin has less pigmentation than someone without the condition. read more