Homozygous substitution of adenine by guanine mutation has been found in DBT gene at 1199 nucleotide position (p. N400S 1199 A-G). No mutations were identified in BCKDH and BCKDHB genes. The identified mutation (1199 A-G) is a new mutation and has not been included in any literature. This mutation disrupts the metabolism of valine, leucine and isoleucine amino acids and leads to maple syrup disease. The presence of maple syrup disease in Azerbaijan population confirms the importance of screening test of newborns for respective disease.