Fukui S, et al. - Authors gauged the effect of renal involvement at diagnosis on the prognosis of patients with antineutrophilic cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Nonetheless, higher ages, lower C3 levels at diagnosis, and poorer prognoses were seen in patients with renal involvement, multivariable analysis demonstrated that the C3 level and age at diagnosis, but not renal involvement, contributed significantly to overall survival. The association between C3 hidden behind renal involvement and AAV prognosis was demonstrated in the findings.