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Paroxysmal nocturnal hemoglobinuria (PNH), previously Marchiafava–Micheli syndrome, is a rare, acquired, life-threatening disease of the blood characterized by destruction of red blood cells by the complement system, a part of the body's intrinsic immune system. This destructive process is a result of a defect in the formation of surface proteins on the red blood cell, which normally function to inhibit such immune reactions. Since the complement cascade attacks the red blood cells throughout the circulatory system, the hemolysis is considered an ''intravascular'' hemolytic anemia. Other key features of the disease, notably the high incidence of thrombosis, are not totally understood. PNH is the only hemolytic anemia caused by an ''acquired'' (rather than inherited) intrinsic defect in the cell membrane (deficiency of glycophosphatidylinositol leading to absence of protective proteins on the membrane). It may develop on its own ("primary PNH") or in the context of other bone marrow disorders such as aplastic anemia ("secondary PNH"). Only a minority (26%) have the telltale red urine in the morning that originally gave the condition its name. Allogeneic bone marrow transplantation is the only curative therapy, but has significant rates of both mortality and ongoing morbidity.〔 The monoclonal antibody eculizumab is effective at reducing the need for blood transfusions and improving quality of life. It, however, does not appear to change the risk of death or blood clots and has an extremely high price, with a single year of treatment costing at least $440,000.〔 ==Signs and symptoms== The classic sign of PNH is red discoloration of the urine due to the presence of hemoglobin and hemosiderin from the breakdown of red blood cells. As the urine is more concentrated in the morning, this is when the color is most pronounced. This phenomenon mainly occurs in those who have the primary form of PNH, who will notice this at some point in their disease course. The remainder mainly experience the symptoms of anemia, such as tiredness, shortness of breath, and palpitations.〔 A small proportion of patients report attacks of abdominal pain, difficulty swallowing and pain during swallowing, as well as erectile dysfunction in men; this occurs mainly when the breakdown of red blood cells is rapid, and is attributable to spasm of smooth muscle due to red cell breakdown products.〔 Forty percent of people with PNH develop thrombosis (a blood clot) at some point in their illness. This is the main cause of severe complications and death in PNH. These may develop in common sites (deep vein thrombosis of the leg and resultant pulmonary embolism when these clots break off and enter the lungs), but in PNH blood clots may also form in more unusual sites: the hepatic vein (causing Budd-Chiari syndrome), the portal vein of the liver (causing portal vein thrombosis), the superior or inferior mesenteric vein (causing mesenteric ischemia) and veins of the skin. Cerebral venous thrombosis, an uncommon form of stroke, is more common in those with PNH.〔 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「paroxysmal nocturnal hemoglobinuria」の詳細全文を読む スポンサード リンク
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