MSUD is caused by mutations in genes that encode the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), a crucial enzyme complex needed to degrade the branched-chain amino acids (BCAAs) leucine, isoleucine, and valine. When BCKDC is deficient or defective, these amino acids and their corresponding keto acids accumulate in the blood, leading to toxic effects. The condition is genetically inherited in an autosomal recessive pattern, meaning that a child must inherit two defective copies of the gene, one from each parent, to exhibit the disease.
