Disclosure of potential conflict of interest: J. S. Orange has received consultancy fees from Baxter Healthcare, ADMA Biologics, ASD Healthcare, CSL Behring, and Atlantic Research; has provided expert testimony for the State of Arizona; has received research support and lecture fees from CSL Behring; has patents with Children's Hospital of Philadelphia; and has received royalties from UpToDate, Springer, and UniMed. The rest of the authors declare that they have no relevant conflicts of interest.