Given the central role of FH in regulation of complement amplification (Fig. 1), proper functioning of this soluble inhibitor is crucial, as exemplified by human pathologies associated with FH, including those with mutations and polymorphisms in the CFH gene; e.g. typical and atypical hemolytic uremic syndrome (HUS and aHUS, respectively) [13, 26–28], age-related macular degeneration (AMD) [29–31] and dense deposit disease (DDD) [32, 33]. The gene discussed is FH; the disease is hemolytic-uremic syndrome.