枫糖浆尿症(MSUD)，又称为支链酮酸尿 ，是一种体染色体隐性遗传的支链氨基酸代谢异常疾病， 也是有机酸血症的一种；这个症状的名称是由婴儿尿液带甜的气味而来。

枫糖浆尿症主要是由支链α-酮酸脱氢酶复合物所引起的代谢障碍造成支链胺基酸的堆积(白胺酸，异白胺酸和缬胺酸)而他们的有毒副产物(酮酸)则会在累积在血液和尿液里。这个蛋白质复合体主要有四个特定的亚基 E1α, E1β, E2, 和E3，而E3次单元是由丙酮酸脱氢酶复合体和丙戊二酸去氢酶复合体组成的。 任何的酵素次单元基因突变都可能导致枫糖浆尿症。

Maple syrup urine disease (MSUD), also called branched-chain ketoaciduria, is an autosomal recessive metabolic disorder affecting branched-chain amino acids. It is one type of organic acidemia. The condition gets its name from the distinctive sweet odor of affected infants' urine, particularly prior to diagnosis, and during times of acute illness.