C3 and acute kidney injury: In our cohort, arguments in favor of IRGN-IgA are: older age (89% were over 50 vs < 30 in most patients with IgAN); nephrotic range proteinuria (70% in our cohort but rare in patients with IgAN); low C3 (16% in our cohort and usually normal in IgAN); severe acute renal failure (all cases except for one in our cohort but uncommon in IgAN).