[The spleen in non-malignant haematological disorders]

The spleen functions as a filter of the circulating blood, removing aging or abnormal red blood cells, intraerythrocyte inclusions as well as foreign particals. As the spleen is composed of lymphocytic tissue, circulatory elements and mononuclear phagocytic cells it plays an important role in the nonspecific as well as the specific immune response. Additionally, the spleen serves as a reservoir for circulating blood cells, especially platelet sequestration by the spleen is well do cumented. The spleen produces blood cells during fetal development and in certain haematological disorders such as myelofibrosis. The destruction of red blood cells within the splenic cords releases iron in the circulation, which is recycled and used to manufacture new erythrocytes in the bone marrow. In several non-malignant haematological disorders antibody-coated cells are cleared from the circulation by phagocytic cells of the spleen. This involves erythrocytes in autoimmunhaemolytic anaemias, platelets in immunthrombocytopenia and neutrophils in Felty syndrome. In hereditary spherocytosis the spleen destroys the resulting defective, spherical red cells. In pyruvate kinase deficiency impaired production of adenosine triphosphate leads to destruction of red blood cells in the spleen or in the liver. In sickle cell anaemia the defective erythrocytes cause sludging and thrombosis in small vessels with infarcts for instance in the spleen, which over time can result in autosplenectomy. In thalassaemia major abnormal haemoglobin forms protein precipitates in the red cells with development of a severe hypochromic anaemia with haemolysis and intramedullary inef fective erythropoiesis. Therapeutic splenectomy can be an option in all of these mentioned non-malignant haematological disorders. The rationale and the pathophysiology of its role in thrombotic thrombocytopenic purpura is probably at least well understood. The use of new and effective drugs such as the monoclonal antibody rituximab or thrombopoietin agonists in immunthrombocytopenia as well as the option of a laparoscopic rather than an open splenectomy have changed our view on benefits and risks of splenectomy in recent years. To minimize these risks such as overwhelming postsplenectomy infection or abdominal vein thrombosis, prophylactic vaccination, postoperative thromboembolism prophylaxis and patient education is mandatory.