Thrombotic thrombocytopaenic purpura (TTP) is a rare but serious medical condition. Its incidence is increased in HIV infection, where it is most common in patients with CD4 counts below 100 cells/mm3. Among HIV-positive people, it occurs mainly in females of African origin. TTP is usually fatal if left untreated.

In the general population, the number of new cases per year is around 3.8 per million people. In HIV-positive people, its incidence is 24 to 40 times higher[1]