MMUT and autosomal recessive disease: Methylmalonic acidemia (MMA) is an autosomal recessive inherited disorder that is characterized by the abnormal accumulation of methylmalonyl-CoA and methylmalonic acid in body fluids, which is caused by either a defect in methylmalonyl-CoA mutase (MCM, EC 5.4.99.2) or a defect in the transport or synthesis of its cofactor, adenosyl-cobalamin (AdoCbcl) [1, 2].