Phenylketonuria (also known as PKU) is an inherited metabolic disorder which affects the body’s ability to process a protein known as phenylalanine (this form of protein is present in a large proportion of foods). People who are affected by PKU are unable to break down the protein because they have a lack of enzymes known as phenylalanine hydroxylase. Around 1 in 25,000 babies in the USA are born with PKU; many cases can be diagnosed early during pregnancy by means of antenatal screening.
If PKU is diagnosed early it can be treated very effectively; however, if the condition is left untreated, it can contribute to mental retardation; this occurs as a result of a build-up of phenylalanine in the bloodstream. Symptoms of this disorder do not usually present until around three months of age; at this time it is common for children to lose interest in their environment and their development may be delayed. Other symptoms include behavioural problems, dry, irritated skin, seizures and a musty type smell.