Aplastic anaemia: pathogenetic mechanisms and treatment with special reference to immunomodulation

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Abstract
Aplastic anaemia (AA) has been defined as a syndrome in which the presence of pancytopenia is accompanied by marrow hypocellularity. Ample laboratory data and clinical observations continue to make immune mediation of bone‐marrow failure an attractive hypothesis. Recent progress in the practice of bone‐marrow transplantation has led to a survival rate of approximately 80% in the best cases, but such a treatment is only amenable in young patients (< 45–50 years) with HLA‐identical bone‐marrow donors. Anti‐lymphocyte and thymocyte globulin treatment has been surprisingly effective for AA, resulting in transfusion independence in 40–80% of patients. The mechanism of action is unknown, although effects on immunosuppression appear to be the most likely candidates. Long‐term results for patients receiving cyclosporin A treatment will soon be available, and preliminary data show an effect similar to that of antithymocyte globulin. In contrast to successful bone‐marrow transplantation, improvement following immunomodulation leaves quantitative abnormalities in all haematopoietic cell lines, and patients are prone to develop clonal (malignant) disease.