As reported, high‐dose IVIg targeted on C3 is used in dermatomyositis patients,96 eculizumab (a C5 blocker) is used in paroxysmal nocturnal hemoglobinuria, atypical haemolytic uremic syndrome, neuromyelitis optica and myasthenia gravis97 and avacopan (a specific C5aR1 antagonist) is used in antineutrophil cytoplasmic antibody‐associated vasculitis.98 The gene discussed is C3; the disease is dermatomyositis.