Biopterin Defect in Cofactor Biosynthesis (BIOPT-BS)



Biopterin defect in cofactor biosynthesis (BIOPT-BS) is a condition that causes high amounts of phenylalanine and other harmful substances to build up in the body. People with BIOPT-BS are unable to process certain amino acids, a building block of protein. Babies with BIOPT-BS usually appear healthy at birth, but signs of this condition may develop over time. Symptoms include developmental delays, seizures, behavioral problems, poor suckling during feed, trouble regulating body temperature, sleeping longer and more often, and weak muscle tone. Some of these signs may occur when a baby eats foods the body cannot break down. Early detection and proper treatment can often prevent the severe outcomes of BIOPT-BS.

Condition Type:



Biopterin defect in cofactor biosynthesis (BIOPT-BS) is very rare. This condition is considered one form of tetrahydrobiopterin deficiency. Overall, tetrahydrobiopterin deficiency affects 1 in every 1 million newborns.

More Information for Parents:
Also known as:
  • Tetrahydrobiopterin deficiency
  • BH4 deficiency
  • Hyperphenylalaninemia caused by a defect in biopterin metabolism
  • Non-phenylketonuria hyperphenylalaninemia
  • Conditions of biopterin biosynthesis
  • Biopterin cofactor defects
  • Guanosine triphosphate cyclohydrolase 1 deficiency
  • 6-pyruvoyl-tetrahydropterin synthase deficiency

Core Conditions