Although the “imbalanced”, “uncontrolled” or “dysregulated” complement activation has been implicated to be the mechanism of atypical HUS, perhaps “unprotected” endothelium due to loss of CD59 protective effect against C5b-9 could be the mechanism leading to endotheliopathy, not only in atypical HUS [53], but also in the critical illnesses. Here, CD59 is linked to hemolytic-uremic syndrome.