Patient cohorts for analysis. The primary outcome analyzed in the USTMA retrospective registry cohort (2004-2019) (A) was clinical relapse (CR) defined as a decrease in platelets of ≤150 × 10⁹/L with or without clinical evidence of ischemic organ injury, confirmed by documentation of severe ADAMTS13 deficiency and occurring after having achieved clinical remission.¹⁹ The prospective Johns Hopkins and University of Minnesota cohort (2004-2023) (B) also included data on serial ADAMTS13 assessments and the primary outcome analyzed in this cohort was overall relapse defined as a composite end point of CR, ADAMTS13 relapse, and preemptive rituximab (RTX) therapy. OR, overall relapse.