Biopterin defect in cofactor regeneration (BIOPT-REG) is a rare genetic disorder causing high levels of the amino acid phenylalanine. Our body breaks down extra protein we eat into its building blocks, the amino acids. Special proteins break down any extra amino acids into harmless products our body can get rid of. If a protein needed to break down phenylalanine is missing, phenylalanine builds up. Symptoms include seizures (epilepsy), muscle weakness (hypotonia), and trouble regulating body temperature. A person with BIOPT-REG also has trouble making chemical signals for the nervous system (neurotransmitters). A lack of neurotransmitters can cause developmental delays, sleep disorders, and behavioral problems.
BIOPT-REG is caused by a mutation (change) to the PCBD1 or QDPR genes. Both genes allow the body to recycle tetrahydrobiopterin (BH4). BH4 helps break down phenylalanine, so if there isn’t enough BH4 recycled, phenylalanine builds up. BHR also makes neurotransmitters. A baby with BIOPT-REG appears healthy until the level of phenylalanine gets too high, usually around 4 months.
BIOPT-REG is an autosomal recessive disorder, meaning both copies of either PCBD1 or QDPR genes must be changed to have symptoms. High levels of phenylalanine in the blood may suggest BIOPT-REG. Other genetic disorders also cause high levels, so genetic testing is needed to confirm the diagnosis. Treatment for BIOPT-REG includes supplements to increase BH4 levels. Many babies are screened for BIOPT-REG at birth so treatment can begin early, but newborn screening conditions vary by state. For more information, visit Baby’s First Test. If your baby has been diagnosed with BIOPT-REG, talk with their doctor about the most current treatment options. Genetic counselors and support groups are also good sources of information.