C2 and age-related macular degeneration: Two genes at this locus (ARMS2 and HTRA1) have been investigated as the source of the AMD risk.[51], [52] Additional AMD risks have been reported for other genes involved in the complement pathway including C2/CFB; C3; C5; C7; SERPING1; CFHR1 +3; CFHR2,4,5; CFI [53]–[60].