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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 Last updated on 05-01-20
Infants with tetrahydrobiopterin (BH4) deficiency typically appear normal and healthy at birth. Neurological signs and symptoms usually become apparent over time, and can range from mild to severe. These may include abnormal muscle tone; poor sucking and coordination; seizures; and delayed motor development. Other manifestations may include decreased spontaneous movements and difficulty swallowing.
Without early and appropriate treatment, signs and symptoms progress and affected individuals may experience irreversible intellectual disability, behavioral problems, an inability to control body temperature, and even death in severe cases.
Last updated on 05-01-20
Feeding problems are common in babies with BH4 deficiency and may include poor sucking and/or difficulty swallowing.
While failure to thrive is not necessarily a primary feature of BH4 deficiency, it may be a secondary complication. Feeding difficulties can cause failure to thrive. If an affected infant does not feed appropriately, he/she may fail to gain weight and/or grow at the expected rate.
Last updated on 05-01-20
The Newborn Screening Coding and Terminology Guide created by the National
Library of Medicine (NLM) at the National Institutes of Health (NIH) promotes
and facilitates the use of electronic health data standards in recording and
transmitting newborn screening test results. The Web site includes standard
codes and terminology for newborn tests and conditions for which they screen,
and links to related sites. Click on the links to view details for this
Disorders of biopterin biosynthesis
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Last updated on 04-27-20
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