Phenylketonuria (pronounced fee-nill-key-toe-NURR-ee-uh) or PKU is an inherited disorder of metabolism that can cause mental retardation if not treated.  In PKU, the body can’t process a portion of the protein called phenylalanine (Phe), which is in almost all foods.  If the Phe level gets too high, the brain can become damaged.

For more information on Phenylketonuria, please refer to-http://www.nichd.nih.gov/health/topics/phenylketonuria.cfm