Patients with DM/TMA had a shorter time since disease onset (p = 0.033), lower levels of C3 (p = 0.07) and C4 (p = 0.046), as well as higher leukocyte (p = 0.044), neutrophil (p = 0.033), and creatine phosphokinase (CK) levels (p = 0.005). Here, C4A is linked to dermatomyositis.