Abstract: Methylmalonic aciduria (MMA) is an autosomal recessive disorder of cobalamin (cbl) metabolism.Cobalamin C (cblC) disease is the most common type of MMA and is characteristically concurrent with homocystinemia (HCY) due to impaired synthesis of two active forms of cbl,namely adenosylcobalamin (AdoCb1) and methylcobalamin (MeCbl).