What is PKU?

Phenylketonuria, commonly known as PKU, is a hereditary disease that causes an increase in a substance called phenylalanine in the blood. Phenylalanine is the building block of proteins obtained with the nutrients ingested. It is also found in some artificial sweeteners. Untreated PKU disease can cause phenylalanine to rise to harmful levels in the body, resulting in other serious health problems, especially mental disability.

PKU has symptoms ranging from mild to severe. The most severe form of the disease is known as classical PKU. Babies with classic PKU look normal until they are several months old. If left untreated, permanent mental disability develops. Seizures, delayed development, behavioral problems, and psychiatric disorders are common. In untreated individuals, a mold-like odor may be felt caused by excessive phenylalanine in the body. Children with classic PKU may have softer skin and hair than other family members unaffected by the disease, as well as skin disorders such as eczema.

Sometimes there may be a small risk of brain damage in species that are rarely seen as different PKU or non-PKU hyperphenylalaninemia. People with very mild cases can be content with a low phenylalanine diet.

Babies born to mothers with PKU and uncontrolled phenylalanine levels pose a significant risk of mental disability as they are exposed to very high phenylalanine before birth. These babies can also have a low birth weight and grow slower than other children. Other characteristic medical problems include heart problems, an abnormally small head size (microcephaly), and behavioral problems. Women with PKU and uncontrolled phenylalanine levels have an increased risk of miscarriage.