BH4 deficiency, BH4 deficient hyperphenylalaninemia
Type of disease: Rare conditions
Tetrahydrobiopterin deficiency, also known as BH4 deficiency, is a genetic condition. This condition results from a mutation or error in one of several genes (GCH1, PCBD1, PTS, or QDPR). The non-working (mutated) genes cause a deficiency in a protein called tetrahydrobiopterin or BH4. Lack of BH4 alters levels of several body substances including neurotransmitters (which transfer signals between cells and the brain) and phenylalanine (the building blocks of proteins). Infants with BH4 deficiency usually appear normal at birth, but symptoms can present themselves over time. These include intellectual disability, movement disorders, difficulty swallowing, seizures, and an inability to control body temperature. BH4 deficiencies can be treated with BH4 supplements (2-20mg/kg per day) or a diet to regulate blood phenylalanine concentration. Many babies are screened to see if they may be affected by BH4 deficiency at birth so treatment can begin early, but the conditions included in newborn screening vary by state by state. For more information, visit Biopterin defect in cofactor biosynthesis and regeneration in Baby’s First Test. This condition is autosomal recessive which means an individual must have two copies of the non-working (mutated) gene that causes the condition. A person with one non-working gene is a carrier of the condition but usually does not have any symptoms. If both parents are carriers, their children have a one in four chance of having the disease. A genetic counselor can help you understand the genetics. Talk with your baby’s doctor and specialists to decide on the best treatment plan. Support groups are also a good source of information.