megaloblastic anemia (disease) Anemia characterized by the presence of unusually large erythroblasts in the bone marrow called megaloblasts. It is usually caused by vitamin B12 or folic acid deficiency. Other causes include toxins and drugs. COHD:435789 DOID:13382 Grasbeck-Imerslund syndrome HP:0001889 ICD10:D53.1 ICD9:281.3 IGS Imerslund-Grasbeck syndrome MGA1 Norwegian type MONDO:0001700 NCIT:C34382 RH-MGA1 SCTID:53165003 UMLS:C0002888 megaloblastic anemia recessive hereditary megaloblastic anemia 1 macrocytic anemia (disease)