Thrombotic thrombocytopenic purpura (TTP) is a rare disorder of the blood coagulation system. In most cases, a lack of the ADAMTS13 enzyme leads to an accumulation of ultra-large von Willebrand factor molecules in the plasma which, in turn, initiate the formation of microscopic thromboses in small blood vessels. TTP is a medical emergency. Timely diagnosis and urgent and effective management are vital – mortality in those untreated is in the region of 90%.The understanding of TTP pathogenesis has increased markedly in recent decades. It is now known that TTP is acquired (immunemediated) or congenital, and that the most common type – the acquired form – predominantly affects women in their 40s. It is also clear that the prompt delivery of plasma exchange saves lives. ’Fast Facts: Thrombotic Thrombocytopenic Purpura’ sets out, in a clear and accessible format, the steps to suspecting, diagnosing and treating this potentially devastating disease. These steps are complemented by clear descriptions of the disease mechanism and epidemiology. Differential diagnosis, which is of the utmost importance for this disease, is explored in detail.