C3 and atypical hemolytic-uremic syndrome: Various mutations in different genes that are associated with aHUS have been documented, which include: loss-of-function mutations in regulatory proteins of complement [complement factor H (CFH), complement factor I (CFI), membrane cofactor protein (MCP/CD46)] and gain-of-function mutations in promoting proteins of complement [complement component 3 (C3), complement factor B (CFB)] [3].