CFHR3 and age-related macular degeneration: Earlier genetic studies identified a common deletion of CFHR1 and CFHR3 and a rare deletion encompassing CFHR1 and CFHR4 as being protective against AMD.16, 17, 18, 19, 20, 21, 22 The mechanism behind these protective associations has been assumed to revolve around the FHR proteins’ being complement activators.25