Methylmalonic acidemia with homocystinuria OMIM:614857 OMIM:277410 OMIM:277400 Methylmalonic aciduria with homocystinuria Methylmalonic acidemia with homocystinuria is an inborn error of vitamin B12 (cobalamin) metabolism characterized by megaloblastic anemia, lethargy, failure to thrive, developmental delay, intellectual deficit and seizures. There are four complementation classes of cobalamin defects (cblC, cblD, cblF and cb1J) that are responsible for methylmalonic acidemia - homocystinuria (methylmalonic acidemia - homocystinuria cblC, cblD cblF and cblJ; see these terms). orphanet Combined defect in adenosylcobalamin and methylcobalamin synthesis ICD10:E72.1 OMIM:277380 MESH:C537359 UMLS:C1848561 Organic aciduria Disorder of cobalamin metabolism and transport Constitutional megaloblastic anemia due to vitamin B12 metabolism disorder