A form of methylmalonic acidemia with homocystinuria, an inborn error of vitamin B12 (cobalamin) metabolism characterized by variable biochemical, neurological and hematological manifestations. The disease is MONDO_0010185 (methylmalonic aciduria and homocystinuria type cblD). Also known as: cblD defect, cobalamin D defect, cobalamin D deficiency, cobalamin d disease, combined defect in adenosylcobalamin and methylcobalamin synthesis, type cblD, methylmalonic aciduria with homocystinuria, type cblD.