The patient was positive for anti-FH IgG1, IgG3, and IgG4, whereas all positive controls from atypical hemolytic uremic syndrome were positive only for anti-FH IgG1 and IgG3, but negative for anti-FH IgG4 (Fig S1). The gene discussed is IGHG3; the disease is atypical hemolytic-uremic syndrome.