MMUT and methylmalonic acidemia: Isolated methylmalonic acidemia (MMA) is a genetically heterogenous group of autosomal recessive inborn errors of metabolism mainly caused by a deficiency of the mitochondrial enzyme methylmalonyl-CoA mutase (OMIM#251000, EC 5.4.99.2) or defects in the synthesis of its cofactor 5’deoxyadenosylcobalamin.