The pathophysiology of aplastic anemia

No single cause can explain aplastic anemia. Two major factors are involved: An intrinsic derangement of hemopoietic proliferation capacity that is essentially compatible with life, but has to be considered a premalignant condition. This primarily diseased tissue can be destroyed by immune mechanisms in an attempt to achieve self-cure. Therefore, immunosuppressive therapy can mitigate this immune reaction but leaves the patient with a poorly proliferating bone marrow that is prone to late complications. The clinical presentation and course depend on the balance of these two major factors: If the immune reaction is strong, acute severe aplasia occurs, whereas in patients with a weak immune reaction the disease will present itself rather as chronic pancytopenia with myelodysplastic traits. Co-involvement of environmental cells in the disease process is an additional factor. Poor production of hemopoietic growth factors may aggravate aplasia and poor immune competence may allow abnormal clones to proliferate. All these pathophysiological factors are genetically determined.