The authors summarize that recent data favor the restrictive use of eculizumab in carefully selected atypical hemolytic uremic syndrome cases, but close monitoring for relapse after drug discontinuation is emphasized. Long-acting C5 monoclonal antibody ravulizumab enables a reduction in the dosing frequency and improving the quality of life in patients with atypical hemolytic uremic syndrome. Here, C5 is linked to hemolytic-uremic syndrome.