CPT® Code 81205

BCKDHB (branched-chain keto acid dehydrogenase E1, beta polypeptide) (eg, maple syrup urine disease) gene analysis, common variants (eg, R183P, G278S, E422X)

The CPT® Code 81205 pertains to the molecular genetic testing of the BCKDHB gene, which encodes the branched-chain keto acid dehydrogenase E1, beta polypeptide. This gene analysis is particularly significant in the context of diagnosing Maple syrup urine disease (MSUD), a rare autosomal recessive disorder. MSUD arises from mutations in the BCKDHB gene inherited from both parents, leading to a deficiency in the enzyme complex responsible for the metabolism of branched-chain amino acids, specifically leucine, isoleucine, and valine. The BCKDHB gene is located on chromosome 6 and has over 40 identified mutations, with common variants including R183P, G278S, and E422X. The incidence of MSUD is estimated at 1 in 185,000 newborns globally, with higher prevalence in certain populations, such as those of Ashkenazi Jewish descent and Old Order Mennonites. The enzyme complex formed by the BCKDHB gene is crucial for breaking down dietary proteins, and its dysfunction leads to toxic accumulation of amino acids and their byproducts, which can severely affect neurological function. Symptoms of MSUD typically manifest in infancy and can include feeding difficulties, developmental delays, lethargy, and seizures, particularly during periods of stress. Genetic testing for the BCKDHB gene is essential for identifying carriers and confirming diagnoses, thereby guiding treatment strategies that focus on dietary management to prevent toxic buildup.