Three patients who discontinued eculizumab harbored abnormalities in complement genes; a patient who subsequently received a diagnosis of STEC-HUS had variants in MCP and CFB genes, another patient had anti-CFH antibodies and CFHR1/3 deletion, and the third patient harbored variants in CFH and MCP (Table 1). The gene discussed is CFHR1; the disease is hemolytic-uremic syndrome.