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Biopterin defect in cofactor biosynthesis

(BIE-ahp-tuhr-in • DEE-fekt • in • koh-fak-tuhr • BIE-oh-SIN-thuh-SIS)

General Condition Information

Other Names

  • Benign hyperphenylalaninemia (due to biopterin defect in co-factor biosynthesis)
  • Biopterin cofactor biosynthesis defect
  • Biopterin defect of cofactor biosynthesis
  • Defect of biopterin cofactor biosynthesis
  • Defects of biopterin cofactor biosynthesis
  • Tetrahydrobiopterin deficiency

Condition Type

Birth Prevalence

  • This condition is one type of a group of rare conditions known as tetrahydrobiopterin deficiencies. Fewer than 10 babies are born with tetrahydrobiopterin deficiencies each year in the United States.

Screening Finding

High levels of phenylalanine

What is Biopterin defect in cofactor biosynthesis

Biopterin defect in cofactor biosynthesis is an inherited (genetic) condition that increases levels of a substance called phenylalanine in the blood. Phenylalanine is one kind of amino acid, which are the building blocks of protein. Your body uses amino acids to make other proteins that it needs to function.

Cofactors are substances that help enzymes work. Tetrahydrobiopterin (BH4), which is a type of biopterin, is a cofactor that helps certain enzymes process phenylalanine and important brain chemicals. Your body needs to build and recycle BH4 correctly for these important enzymes to work. Biopterin defect in cofactor biosynthesis occurs when the body cannot build BH4.

Biopterin defect in cofactor biosynthesis is one of a group of conditions called tetrahydrobiopterin deficiencies. Another condition in this group is called Biopterin Defect in Cofactor Regeneration, which occurs when BH4 is not recycled correctly. 

Two enzymes in your body help build BH4. In biopterin defect in cofactor biosynthesis, one of these two enzymes does not work well. Without working BH4, the enzymes that need this cofactor as a helper cannot do important jobs in the body.

Babies with biopterin defect in cofactor biosynthesis cannot break down all of the phenylalanine from the proteins they eat. As a result, phenylalanine builds up to harmful levels in their body. Their body also makes fewer important chemicals for their brain called neurotransmitters. This can cause the signs and symptoms of the condition.

Newborn Screening and Follow-Up

Condition Details

Treatment and Management

It is important to talk to your health care provider about which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition.

Treatments may include the following:

  • Restricted diet that avoids foods with phenylalanine
  • Medical formula and foods
  • BH4 supplements to reduce phenylalanine levels
  • Medicine to help/increase neurotransmitter levels

Children who receive early and ongoing treatment for biopterin defect in cofactor biosynthesis can have healthy growth and development.

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