PD BTH is typically associated with complement-amplifying conditions such as infection, surgery, and other events that may trigger inflammation and complement activation.50,63 Of the five BTH events occurring in ravulizumab-treated patients across the studies, none was temporally associated with suboptimal C5 inhibition (free C5 ⩾ 0.5 mg/mL); four (80%) were temporally associated with complement-amplifying conditions.61 This evidence concerns the gene C5 and infection.