AA is an acquired idiopathic form of bone marrow aplasia with peripheral pancytopenia and empty bone marrow. Its etiology is a cell mediated autoimmune process damaging the hemopoietic stem cell. The disease is very rare (incidence 2/1'000'000/year). Untreated, the course of the disease is lethal mainly due to infections (fungi) . Affected are primarily young adults. There is no biological test to prove an autoimmune origin. Therefore, the diagnosis relies on the bone marrow examination and the exclusion of alternative causes of bone marrow aplasia such as hereditary, drug-related, toxic or viral.
The patients show symptoms of pancytopenia with fatigue, weakness, and exercise intolerance as signs of anemia, hemorrhages as sign of thrombocytopenia and infections as sign of neutropenia/agranulocytosis. The course of the disease is usally slowly developing over weeks to month and becomes chronic if untreated.
The treatment is based on the combination of immunosuppression with Cyclosporin A (Sandimmun neoral) and anti-thymocyte-globulin (serum of horses against human T-cells) or on an allogenic hematopoietic stem cell transplantation. In children and younger adults, stem cell transplantation is preferred, in older adults immunosuppression.
There is pancytopenia with anemie, reticulopenia, neutropenie and thrombocytopenia. There ar no signs of dysplasia. Based on the blood cell counts, aplastic anemia is divided into three grades of severity:
|Non-severe apalstic anemia||nsAA||< 1.0 x109/L||< 60 x109/L||< 100 x109/L|
|Severe apalstic anemia||SAA||< 0.5 x109/L||< 40 x109/L||< 20 x109/L|
|Very severe apalstic anemia||vSAA||< 0.2 x109/L||< 40 x109/L||< 20 x109/L|
The bone marrow is hypocellular to aplastic. In very severe types, the hematopoietic tissue is completely lacking. Occasionally, foci of remaining hematopoiesis are found in an otherwise empty bone marrow. A relative increase of lymphocytes are typically found as sign of an autoimmune process. Contrary to the hypocellular myelodysplastic syndrome, the remaininig hematopoiesis is cytologically unobtrusive without signs of dysplasia. The cytogenetic examination of the bone marrow is also helpful in differentiation from myelodysplastic syndromes.