12/22/2020 The authors describe the feasibility of a first-of-its-kind patient-powered natural history registry for studying Castleman disease, a rare hematologic disorder. A traditional registry design was paired with a patient-powered approach, in which patients self-enroll and data collection are centralized. Clinical insights from this study have already supported new treatment guidelines, and the use of a de-identified linkage to a biobank has enabled groundbreaking translational discoveries.