What are common symptoms of phenylketonuria (PKU)?

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. If people with PKU do not restrict the phenylalanine in their diet, they develop severe intellectual and developmental disabilities.

Other symptoms include:

  • Behavioral or social problems
  • Seizures, shaking, or jerking movements in the arms and legs
  • Stunted or slow growth
  • Skin rashes, like eczema (pronounced EK-suh-muh)
  • Small head size, called microcephaly (pronounced mahy-kroh-SEF-uh-lee)
  • A musty odor in urine, breath, or skin that is a result of the extra phenylalanine in the body
  • Fair skin and blue eyes, due to the body's failure to transform phenylalanine into melanin, the pigment responsible for a person's coloring1


  1. Genetics Home Reference. (2012). Phenylketonuria. Retrieved June 22, 2012, from https://ghr.nlm.nih.gov/condition=phenylketonuria

top of pageBACK TO TOP