Aplastic anemia is a condition where bone marrow does not produce enough, or any, new cellss to replenish the blood. One known cause is an autoimmune disorder, where the white blood cells attack the bone marrow.

Treating aplastic anemia involves suppression of the immune system, an effect achieved by daily medicine intake, or, in more severe cases, a bone marrow transplant, a curing but risky procedure. An interesting property of bone marrow transplants is the production of new white blood cells, an effect that removes the possibility of rejection. However, newly created white blood cells might reject the whole body instead.

The term 'aplastic' refers to the inability of the marrow to function properly. Anemia is the condition of having fewer blood cells than normal, or fewer than needed to function properly. Typically, anemia refers to low red blood cell counts, but aplastic anemia patients have lower counts on all three blood cell types: red blood cells, white blood cells, and platelets.