The term phenylketonuria refers to a genetic disorder characterized by elevated levels of a substance called phenylalanine in the blood. The disorder affects our body’s natural capacity to process phenylalanine (Phe), an integral part of proteins.  It can lead to brain damage and severe intellectual disability. Babies born in the U.S. hospitals undergo compulsory screening test for phenylketonuria. Treatment is made easy if it is diagnosed at the earliest.

Phenylalanine hydroxylase enzyme helps our body to absorb phenylalanine obtained through the diet. Genetic mutation inactivates this enzyme in those who have phenylketonuria resulting in high levels of phenylalanine in blood.


Phenylketonuria doesn’t show up any symptoms if treated early. If proper treatment is not given, newborns will develop symptoms within a couple of months. Untreated phenylketonuria leads to brain and nervous system disorder resulting in seizures, delayed growth, mental retardation, social and behavioral problems, abnormal head size, skin rashes, hyperactivity, mouse-like urine odor, tremors and jerks in the arms and legs.

How is phenylketonuria diagnosed?

A routine blood test is executed to diagnose phenylketonuria. The test checks for the phenylalanine level in blood. Phenylketonuria is confirmed if the phenylalanine level in blood is abnormally high. You would be referred to a phenylketonuria specialist. A dietician’s advice is very much needed to modify the patient’s diet. Regular blood tests are necessary throughout the life to check for the phenylalanine levels and to measure treatment response.

How is phenylketonuria treated?

A low protein diet is recommended to treat phenylketonuria. There are specific diet formulas for each age group. The diet includes low-protein breads, pastas, cereals, fruits, vegetables etc. Children who followed this low protein diet soon after their birth grows normally. It is important that they should follow the diet throughout their lives. Regular intake of dietary supplements is needed to get essential nutrients that the low-protein diet lacks. These supplements are available in several forms such as powders, drinks and tablets. The treatment cost depends on the the diet formula that you choose for the treatment.

Can phenylketonuria be prevented?

Nothing can be done to prevent this genetic disorder.