In a study involving 120 patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, plasma levels of C3a, C5a, soluble C5b-9, and Bb were significantly higher in the active stage of the disease along with lower levels of properdin pointing toward the involvement of the alternative pathway in the pathophysiology of ANCA-associated vasculitis [6]. The gene discussed is C5AR1; the disease is anti-neutrophil cytoplasmic antibody-associated vasculitis.