Eculizumab, a monoclonal anti-C5 antibody, has been reported to be effective in controlling thrombotic microangiopathy and improving renal function, and is used in clinical practice to treat paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic-uremic syndrome (aHUS). The gene discussed is C5; the disease is thrombotic microangiopathy.