As mentioned previously, the term non-megaloblastic macrocytic anemia is given to an anemia associated with larger than normal cells (MCV>100 fL but generally < 110 fL), but is not caused by a nuclear maturation defect. There are several different causes of non-megaloblastic macrocytic anemia. Table 2 lists a number of these causes. This course will then focus on only a few of them, namely alcoholism, drugs, and MDS.
Table 2. Causes of Non-Megaloblastic Macrocytic Anemia.Cause of
Non-Megaloblastic Macrocytic Anemia | Comments |
| Reticulocytosis | Not an abnormal finding if compensating for anemia (reticulocytes are slightly larger than mature RBCs). |
| Alcoholism | Toxic effects lead to vacuolization of developing erythrocytes, thus producing macrocytes. Note: Alcohol can also cause other types of anemia including megaloblastic anemia and microcytic anemia. |
| Drugs | Various effects depending on the drug; some drugs can occasionally also lead to megaloblastic anemia. |
| Liver Disease | May be due to increased deposition of cholesterol on RBC membranes. Liver disease can also occasionally cause megaloblastic macrocytic anemia. |
| Myelodysplastic Syndromes (MDS) | Mutations leading to ineffective erythropoiesis (also involves other cell lines). |
| Hypothyroidism | Anemia in hypothyroidism can also be normocytic. |
| Other rare causes | Rare causes include Congenital Dyserythropoietic Anemia, Diamond Blackfan Syndrome, copper deficiency, and others. |
