This biopsy is from a young adult patient with IgA nephropathy (the immunofluorescence image in Fig. 2 shows 2+ mesangial IgA deposits). While both glomeruli show endocapillary hypercellularity, the arrow indicates one glomerulus with a cellular crescent (Fig. 1). The recently updated Oxford classification of IgA nephropathy recommends that the frequency of crescents (cellular and/or fibrocellular) be added as the “C” in the MEST-C score (see reference). Although randomized clinical trials are still needed to determine optimal therapy, a C1 score (crescents in <25% of glomeruli) identifies patients at risk for poor renal outcome if not treated with immunosuppression, and a C2 score (crescents in >25% of glomeruli) identifies patients at risk for poor renal outcome even with the addition of immunosuppressive therapy.
Reference:
Trimarchi H et al. Oxford Classification of IgA nephropathy 2016: an update from the IgA Nephropathy Classification Working Group. Kidney Int. 2017 May; 91(5):1014-1021.
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