Conflicts of interest Dr Siebenhaar has received honoraria (advisory board, speaker) and/or institutional grant/research support from Allakos, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, Celldex, Cogent, Escient, GSK, Granular, Invea, Moxie, Noucor, Novartis, Sanofi/Regeneron, Telios, and Third Harmonic Bio. Dr Broesby-Olsen has received honoraria from Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, Novartis, Thermo Fisher; and is a study steering committee member for Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi. Dr Castells has served as a consultant for Blueprint Medicines Corporation and is a PI on several clinical trials for Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi. She has received author fees from UpToDate and the Editorial Board for Annals of Allergy, Asthma & Immunology. Dr George has received consulting fees and is a study steering committee member for Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, BMS/Celgene, Cogent Biosciences, and Incyte. Dr Livideanu has received consultancy fees from Lilly, Novartis, UCB, and research support from Novartis. She is a member of the steering committee for an AB Science study. Dr Álvarez-Twose has received research funding from Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi and has received advisory board or speaker fees from Blueprint Medicines Corporation and Novartis. Dr Panse has received honorarium fees from Apellis, Alexion, AstraZeneca, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, BMS, Cogent, F. Hoffmann-La Roche, Grünenthal, MSD, Novartis, Omeros, and SOBI; and has served on the speaker's bureau of Alexion, Boehringer Ingelheim, Chugai, Novartis, Omeros, Pfizer, and SOBI and is a study steering committee member for Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi and Omeros. Dr Barete is PI and coordinator for several clinical trials for Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi and PI for Cogent Biosciences trials in France. He has received fees for symposiums and scientific boards from Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi. He holds a consultancy agreement with Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi. He has received additional fees from AbbVie, Amgen, Novartis, Leo Pharma, and Cogent Biosciences laboratories. Dr Reiter has received research funding, served on advisory boards, received honoraria and funding to cover travel expenses from AbbVie, AOP, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, BMS, GSK, Incyte, and Novartis. Dr Dybedal has received advisory board fees from Novartis and Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi. Dr Akin has received consulting fees and research support from Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, and Cogent Biosciences, and consulting fees from Novartis. Dr Van Daele received speaking fees from Novartis. Dr Radia has been a clinical advisory board/study steering group member (EXPLORER/PATHFINDER) for Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi; a study steering committee member for Cogent Biosciences; and has been involved in educational events and advisory boards for Novartis; received author fees for Medscape cases. Dr Cerquozzi has served on advisory boards and received honorarium from AbbVie, BMS, Celgene, Novartis, Jazz, GSK, Paladin, Pfizer, and Medison. Dr Ustun has received honoraria from Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, and Takeda for a speaker bureau, participated on an advisory board for Cogent, and has a nonpaid role in The Mastocytosis Society. Dr Sabato's institution has received research funding from Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi for clinical trials. He received payment or honoraria for lectures, presentations, speakers’ bureaus, manuscript writing or educational events from Blueprint Medicines Corporation, Novartis, and Cogent Biosciences. He participated on a Data Safety Monitoring Board or advisory board for Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi and Cogent Biosciences. Dr Gotlib is the Chair of the Response Adjudication Committee, has received research funding, served on advisory boards, and received honoraria and funding to cover travel expenses from Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi. Dr Gotlib has received research funding, is the co-chair of the study steering committee, and has honoraria for these roles and serves on advisory boards for Deciphera. Dr Rafferty has received fees for advisory boards and speaker fees from AbbVie, AstraZeneca, and Novartis. Dr DeAngelo has served as a consultant for Amgen, Autolus, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, Gilead, Kite, Jazz, Novartis, Pfizer, Servier, and Takeda; and received research funding from AbbVie, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, GlycoMimetics, and Novartis. Dr Schafhausen has received research funding from Apellis Pharmaceuticals, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, BMS/Celgene, Incyte, MSD, Novartis, AstraZeneca, GSK, AdlaiNortye Co, Ltd, KARTOS Therapeutics, MorphoSys AG/Constellation Pharmaceuticals; fees for advisory boards and speaker fees from Alexion, AOP Orphan, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, BMS/Celgene, Merck Serono, MSD, Novartis, Pfizer, Roche, Swedish Orphan Biovitrum, Incyte; and funding to cover travel expenses from AOP Orphan, Novartis, and BMS/Celgene. Dr Ogbogu has received research support from AstraZeneca, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, and GSK. Dr Rets received honoraria from Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi. Dr Lin, Dr Bidollari, Dr Hong, Dr Shaheen, and Dr Lampson are employees and equity holders of Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi. Dr Hartmann has received honoraria (advisory board, speaker) and/or institutional grant/research support from ALK, Allergopharma, Almirall, BioCryst, Blueprint Medicines Corporation, a wholly-owned subsidiary of Sanofi, Cogent, Galderma, KalVista, Leo, Menarini, Novartis, Pfizer, Sanofi, Takeda, and Thermo Fisher. Drs Ungerstedt, Florell, and Wada have no conflicts of interest to declare.