IgA nephropathy (IgAN), or Berger’s disease, is the most common primary glomerulopathy worldwide. It is characterized by dominant mesangial deposition of immunoglobulin A1 (IgA1), typically of the galactose‐deficient form (Gd‐IgA1), which triggers the formation of circulating immune complexes and subsequent glomerular inflammation. Clinical presentation includes hematuria, proteinuria, and, in severe cases, progressive renal failure. A rare variant is the extracapillary or crescentic form, which follows an aggressive course. We report the case of a 52‐year‐old woman with a history of Stage II right‐sided infiltrating ductal breast carcinoma, treated in 2023 with radical mastectomy, AC‐T chemotherapy, and radiotherapy. Complete oncologic remission was confirmed by SPECT imaging. In January 2025, with a known baseline creatinine of 1.2 mg/dL, the patient presented with macroscopic hematuria, hypertension, and rapid decline in renal function. Workup revealed subnephrotic proteinuria (1854 mg/24 h), active urinary sediment with 65% dysmorphic erythrocytes and red blood cell casts, and a creatinine peak of 4.7 mg/dL. Autoimmune serologies were negative. Kidney biopsy showed IgAN with cellular crescents in 64% of glomeruli and an Oxford classification of M0 E0 S1T1 C2. Immunofluorescence confirmed mesangial IgA and C3 deposits. Despite treatment with intravenous methylprednisolone, cyclophosphamide, and oral prednisone, yet no renal recovery was achieved, and the patient remains on chronic hemodialysis. To our knowledge, this is the first reported case in Bolivia of extracapillary IgAN occurring after breast cancer remission, highlighting a rare clinical association and raising the possibility of an underlying immune‐mediated link between malignancy and crescentic IgAN, without establishing causality.
Montesinos et al. (2026) studied this question.