High levels of methylmalonic acid (MMA) associated with tricarboxylic acids intermediates can be identified in mtDNA depletion syndromes secondary to succinate-CoA ligase ADP-forming subunit beta (SUCLA2) and succinate-CoA ligase GDP/ADP-forming subunit alpha (SUCGL1), as well as in methylmalonic acidurias [48,49]. This evidence concerns the gene SUCLA2 and Methylmalonic aciduria.