PKU

Phenylketonuria (often abbreviated to PKU) is an inherited disorder that increases the levels of a substance called phenylalanine in the blood. Phenylalanine is a building block of proteins (an amino acid) that is obtained through the diet. It is found in all proteins and in some artificial sweeteners. If PKU is not treated, phenylalanine can build up to harmful levels in the body, causing intellectual disability and other serious health problems.

Causes

The cause of PKU is a defect in the gene that helps create the enzyme needed to break down phenylalanine. Without the enzyme necessary to process phenylalanine, a dangerous buildup can develop when a person with PKU eats foods that are high in protein, such as milk, cheese, nuts or meats. PKU is an autosomal recessive disorder, which means both parents must pass on the defective gene for their child to develop the condition.

Symptoms

The signs and symptoms of PKU can range from mild to severe. The most severe form of this disorder is known as classic PKU. Infants with classic PKU appear normal until they are a few months old. Without treatment, these children develop permanent intellectual disability. Seizures, delayed development, behavioral problems, and psychiatric disorders are also common with this disorder. Less severe forms of PKU, sometimes called variant PKU and non-PKU hyperphenylalaninemia, have a smaller risk of brain damage.

Diagnosis

PKU is commonly diagnosed through newborn screening tests. The diagnosis is confirmed by testing the levels of phenylalanine in the blood. High levels of phenylalanine can be detected in the blood of a newborn baby.

Treatment

The main treatment for PKU is a diet of low-protein foods. There are special formulas for newborns. For older children and adults, the diet includes many fruits and vegetables. It also includes some low-protein breads and pastas, as well as certain cereals, sweets and beverages. People with PKU must monitor their protein intake, keeping their consumption of phenylalanine within safe levels.

See also

• Genetic disorder
• Amino acid
• Enzyme
• Protein
• Autosomal recessive inheritance

PKU Resources
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