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Bone marrow suppression or myelotoxicity (adjective myelotoxic) or myelosuppression is the decrease in production of cells responsible for providing immunity (leukocytes), carrying oxygen (erythrocytes), and/or those responsible for normal blood clotting (thrombocytes).〔(【引用サイトリンク】title=bone marrow suppression )〕 Bone marrow suppression is a serious side effect of chemotherapy and certain drugs affecting the immune system such as azathioprine.〔(Azathioprine side effects )〕 The risk is especially high in cytotoxic chemotherapy for leukemia. Non-steroidal anti-inflammatory drugs, in some rare instances, may also cause bone marrow suppression. The decrease in blood cell counts does not occur right at the start of chemotherapy because the drugs do not destroy the cells already in the bloodstream (these are not dividing rapidly). Instead, the drugs affect new blood cells that are being made by the bone marrow.〔(Bone marrow suppression )〕 When myelosuppression is severe, it is called myeloablation.〔(Dictionary of Cancer Terms: myelosuppression )〕 Because the bone marrow is the manufacturing center of blood cells, the suppression of bone marrow activity causes a deficiency of blood cells. This condition can rapidly lead to life-threatening infection, as the body cannot produce leukocytes in response to invading bacteria and viruses, as well as leading to anaemia due to a lack of red blood cells and spontaneous severe bleeding due to deficiency of platelets. Parvovirus B19 inhibits erythropoiesis by lytically infecting RBC precursors in the bone marrow and is associated with a number of different diseases ranging from benign to severe. In immunocompromised patients, B19 infection may persist for months, leading to chronic anemia with B19 viremia due to chronic marrow suppression.〔(Parvovirus B19 - BASICS )〕 Thiazide diuretics can also lead to bone marrow suppression as an adverse effect. ==Treatment== Bone marrow suppression due to azathioprine can be treated by changing to another medication such as mycophenolate mofetil (for organ transplants) or other disease-modifying drugs in rheumatoid arthritis or Crohn's disease. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「bone marrow suppression」の詳細全文を読む スポンサード リンク
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