C4A and systemic lupus erythematosus: In all tissues, the C4A (median p = 1.2 × 10−15, 28 tissues), CYP21A1P (median 3.3 × 10−15, 12 tissues), and C4B (median p = 2.7 × 10−15, 6 tissues) genes were the top pleiotropic associations with SLE.