CFH and hemolytic-uremic syndrome: Multiple theories including the role of Streptococcus pneumoniae (neuraminidase, surface protein C), immunological factors (Factor H, complement dysregulation), and host genetic factors (complement gene defects) have been proposed for the pathogenesis of Sp-HUS and it remains unclear if any single factor, or a combination of these factors, contributes to the development of Sp-HUS.