Most of the identified genetic variations have been described before as risk factors for other diseases associated with a dysregulated complement system (aHUS and/or age-related macular degeneration), and functional studies showed that these aberrations either influence the binding capacity of a complement to C3b regulators or affect the inactivation of C3 [5, 8–10, 43–45]. Here, C3 is linked to age-related macular degeneration.