Hemolytic uremic syndrome Mutation of the factor H gene results in impaired C3 convertase activity and is associated with atypical hemolytic uremic syndrome (aHUS) wherein hemolytic anemia, thrombocytopenia and acute renal failure develop. It is thought that the mutant Factor H protein binds less efficiently to C3b and C3d on endothelial cells and, as a result, there is increased vascular damage, especially to endothelial cells, with resultant intravascular deposition of fibrin. However, recently, mutations in Factor I, Factor B and CD 46 have been implicated in aHUS patients (Botto et al. 2009; Pettigrew et al. 2009 ).