Study of Global Coagulation Tests in Patients With Paroxysmal Nocturnal Haemoglobinuria

Paroxysmal nocturnal haemaoglobinuria (PNH) is a rare disease which results in breakdown of the red blood cells and bone marrow failure. It is associated with an increased risk of blood clots. Until recently, treatment has been with blood transfusions and in patients with a blood clot, blood thinners. A new treatment called eculizumab is now standard for patients who require regular blood transfusions. It works in the majority of patients by preventing the breakdown of red blood cells. This can eliminate the need for blood transfusion and reduce the risk of blood clots. It is not well understood why patients with PNH are at high risk of blood clots. The investigators plan to use specialised blood tests to assess the stickiness of the blood before starting eculizumab treatment and monthly after starting treatment. The investigators will compare these tests with standard tests of clotting.