 Adult patients across up to 8 participating UK sites presenting with acute TTP and who fall within the study protocol inclusion criteria, as determined by the Lead Consultant Haematologist per institution, will be offered entry into the study. We wish to recruit 40 patients to this study and although the incidence of TTP is low, it is generally considered to be under diagnosed and therefore, underestimated. Recruiting 40 patients is achievable considering the number of patients presenting with acute TTP within the SEE TTP study group over the past 18 months. Some TTP patients may be unconscious or may have a neurological dysfunction associated with acute TTP, such as personality or memory symptoms. In these cases, consent will be requested from the patients legal representative in compliance with the International Conference on Harmonisation ICH guidance for Good Clinical Practice GCP. 