This research study encompasses the hereditary methylmalonic acidemias and cobalmin deficiency disorders. These metabolic disorders are genetically heterogeneous and collectively represent an important subset of the organic acidemias. We study the hereditary methylmalonic acidemias and cobalmin deficiency disorders via a translational approach that includes a clinical and metabolic evaluation of affected patients and use animal models to examine the disorder in the laboratory. We have developed mouse and worm models of methylmalonic acidemia. The general goal of the research is to define the complications seen in the patients, replicate the findings in mice or other organisms and use the combined information to guide the development and testing of new therapies.