Different studies have highlighted complement activation (e.g. the C5aR1 axis (29)), platelet activation (4), immune-mediated thrombotic mechanisms (6), endothelial dysfunction, antiphospholipid antibody, and renin-angiotensin system dysregulation as important actors of COVID-19-associated coagulopathy (30). This evidence concerns the gene C5AR1 and blood coagulation disease.