Investigator fascination with TTP. Shown are publications retrieved from PubMed using the search term “thrombotic thrombocytopenic purpura.” Given the annual incidence of TTP (idiopathic TTP, 4.5 cases/million; idiopathic TTP with severe ADAMTS13 deficiency, 1.72 cases/million²⁴ ), there seem to exist almost more publications than cases. PEX indicates plasma exchange. The pentad of clinical signs of TTP was described by Amorosi and Ultmann,⁵¹  the Canadian plasma exchange study was reported by Rock et al.⁵²