ADAMTS13 and thrombotic thrombocytopenic purpura: Numerous patients with acquired idiopathic (ai)‐TTP have a disintegrin‐like and metalloprotease with thrombospondin type 1 motifs 13 (ADAMTS13) inhibitor and reduced ADAMTS13 activity, which cleaves von Willebrand factor (vWF), resulting in unusually large vWF multimers binding to platelets and causing microvascular thrombi.2