What is phenylketonuria?
A person with phenylketonuria has an inherited illness that prevents the body from breaking down phenylalanine. Phenylalanine is one of the naturally occurring amino acids, which are the building blocks for proteins. As a result, phenylalanine builds up in the bloodstream, and becomes toxic to the brain. About 1 in 16,000 infants in the US is born with phenylketonuria.

What are the symptoms of phenylketonuria?
Symptoms of phenylketonuria in the newborn include excessive sleepiness, lethargy, poor feeding, rash, and an unusual body odor. Symptoms of severe phenylketonuria include tremor, muscle spasms, hyperactivity, mental retardation, and seizures.

How does the doctor treat phenylketonuria?
Treatment for phenylketonuria includes a special diet, tyrosine supplements, biopterin cofactor therapy, sapropterin, and amino acid supplements.