C3 and systemic lupus erythematosus: C3 levels (0.4174 ± 0.04605 vs. 0.5646 ± 0.06724, p = .0072) and C4 levels (0.08030 ± 0.01303 vs. 0.1255 ± 0.01930, p = .0321) were significantly lower in patients with MAS as an initial manifestation of SLE compared with patients with MAS during the course of lupus.