Thrombotic Thrombocytopenic Purpura (TTP) is a rare blood disorder, with between 1.2 and 11 new cases every year per million of the population. It is more common in women than men and, although it can affect people of all ages, the average age of diagnosis is 40 years. TTP episodes are serious and life-threatening. It is considered a medical emergency and it is estimated that 10-20% of acute patients die from TTP, despite currently available treatments. TTP is a lifelong condition, as after their initial diagnosis many patients will experience further episodes of TTP (called relapses).