Faria B, Canão P, Cai Q, et al. - This retrospective cohort analysis was carried out to determine the clinical significance of arteriolar C4d (C4dA) in IgA nephropathy (IgAN) kidney biopsy tissue, given recent investigations have suggested a link between vascular lesions in IgAN biopsies with complement deposition and disease progression. This study included 126 adults diagnosed with IgAN under the Oxford Classification. Multivariable Cox regression analysis was performed to ascertain the link of C4dA and C4dG (glomerular C4d) with baseline clinical and histological features, as well as progressive kidney disease. C4dA was shown to have a link with mean arterial pressure (MAP), arterial intima fibrosis, and chronic microangiopathy. The regression analysis revealed a significant link of C4dA with progressive kidney disease following adjustment for other significant predictors such as baseline eGFR, MAP, and the presence of crescents. Overall, experts suggested that C4dA holds potential as a biomarker for disease progression in IgAN.