In addition, dysfunction of the complement system directly underlies the etiology of several diseases, including paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), glomerulopathies, and CD55 deficiency with hyperactivation of complement, angiopathic thrombosis, and protein-losing enteropathy (the CHAPLE syndrome) [1]. The gene discussed is CD55; the disease is paroxysmal nocturnal hemoglobinuria.