A Novel Entity of Renal Toxicity After Combination Chemotherapy: An Onco-Nephrology Kidney Biopsy Teaching Case.

Renal injury associated with combination cancer therapies represents a growing diagnostic challenge. Kidney biopsy enables early and appropriate detection of these cases, helping in accurate differential diagnosis and individualized management in these increasingly frequent and complex clinical settings. We report a tricky onco-nephrology teaching case involving a 65-year-old woman with recurrent high-grade Müllerian carcinoma who developed progressive kidney dysfunction, arterial hypertension, and new-onset subnephrotic range proteinuria during treatment with carboplatin, gemcitabine, and bevacizumab. Serologic tests were negative for autoimmune, viral, and hematologic causes. Kidney biopsy showed an advanced membranoproliferative pattern with eosinophilic and periodic acid-Schiff positive intracapillary deposits, diffuse endothelial injury, and unusual tubular myelin figures. Two weeks after kidney biopsy, the patient developed cutaneous purpura that shifted the diagnostic framework toward a systemic vasculopathy. This was supported by the ultrastructural evidence of polyclonal IgM-dominant organized intraluminal deposits and consistent with a drug-induced cryoglobulinemic glomerulonephritis superimposed on gemcitabine-induced chronic thrombotic microangiopathy with unexpected renal lipidosis. To our knowledge, this represents the first reported case of this specific renal injury profile in this clinical setting, underscoring the critical role of kidney biopsy in optimizing personalized care within the emerging field of onco-nephrology.