In selected cases, renal biopsy can be safely performed even during active MRSA infection, providing critical diagnostic information to distinguish among potential etiologies such as drug-induced nephrotoxicity, HCV-associated glomerular disease, or primary glomerulopathies that may warrant immunosuppressive therapy. In our case, the biopsy findings-endocapillary hypercellularity with eosinophils and strong, diffuse mesangial C3 deposits-were consistent with IRGN. The gene discussed is C3; the disease is glomerular disorder.