Even though we now have 330 loci, the published genetic association literature largely ignores the probably major impact that the 20 kb complement C4 gene (C4) repeats at 6p21.33 in the HLA region have upon overall SLE risk, because this variation has not yet been established in association studies to reach p < 5 × 10−8 (129). The gene discussed is C4A; the disease is systemic lupus erythematosus.