Question: What is (are) Tetrahydrobiopterin deficiency ?
Answer: Tetrahydrobiopterin (BH4) deficiency is a neurological condition caused by an inborn error of metabolism. BH4 is a substance in the body that enhances the action of other enzymes. Deficiency of BH4 leads to abnormally high blood levels of the amino acid phenylalanine, and low levels of certain neurotransmitters. Signs and symptoms can range from very mild to severe. Affected newborns appear normal at birth, but may begin to experience neurological symptoms such as abnormal muscle tone; poor sucking and coordination; seizures; and delayed motor development. Without early, appropriate treatment, the condition can cause permanent intellectual disability and even death. BH4 deficiency is caused by mutations in any one of several genes including the GCH1, PCBD1, PTS, and QDPR genes. It is inherited in an autosomal recessive manner.Treatment depends on the genetic cause and severity, and may include a low phenylalanine diet; oral BH4 supplementation; and neurotransmitter replacement.
Source: GARD