Eculizumab is a recombinant, humanized, monoclonal immunoglobulin G antibody that blocks the cleavage of C5 to C5b, thus preventing the formation of the proinflammatory peptide C5b and the cytotoxic membrane attack complex C5b-9 (MAC) [2]. Eculizumab is approved for use in aHUS and paroxysmal nocturnal hemoglobinuria (PMH). Here, C5 is linked to paroxysmal nocturnal hemoglobinuria.