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. Here, C4A is linked to systemic lupus erythematosus.