type methylmalonic acidemia with homocystinuria is a form of methylmalonic acidemia with homocystinuria (see this term), an inborn error of vitamin B12 (cobalamin) metabolism characterized by variable biochemical, neurological and hematological manifestations. The disease is Methylmalonic acidemia with homocystinuria, type cblD (Orphanet rare-disease nomenclature id Orphanet_79283). Also known as: CblD defect, Cobalamin D defect, Combined defect in adenosylcobalamin and methylcobalamin synthesis, type cblD, Methylmalonic aciduria with homocystinuria, type cblD.