In an unusual case published in BMC Nephrology, a 75-year-old woman was diagnosed with Granulomatosis with Polyangiitis (GPA) after presenting with a solitary renal mass. GPA is a rare autoimmune disorder characterized by necrotizing granulomatous vasculitis, primarily affecting small-sized vessels in the upper and lower airways and kidneys. Renal involvement in GPA typically manifests as focal segmental necrotizing glomerulonephritis, leading to rapid renal failure. However, the presence of a renal mass in GPA patients is exceptionally rare but can be identifiable.

The patient's condition came to light when an enhanced computed tomography (CT) scan revealed a solitary mass measuring 4 × 3.5 cm in her right kidney. Initially, there were no apparent symptoms or history of sinusitis, rhinitis, cough, or pneumonia, which are suggestive of systemic GPA. To rule out malignancy like renal cell carcinoma or malignant lymphoma, the patient underwent a nephrectomy.
Three months after the surgery, she was admitted again as her serum creatinine levels had risen dramatically from 54.81 μmol/L to 405.76 μmol/L, and her C-reactive protein level was measured at 159 mg/L. However, tests for anti-neutrophil cytoplasmic antibodies against myeloperoxidase and anti-proteinase 3 came back negative. Subsequent histological examinations of the excised renal mass revealed necrotizing granulomatous arteritis in the cortex and medullary vasa recta, along with focal segmental necrotizing glomerulonephritis. Interestingly, there were no signs of vasculitis observed in any areas other than the solitary mass. Based on these findings, the patient was diagnosed with GPA.
Prompt treatment with prednisolone (30 mg/day) was initiated, but unfortunately, her renal function continued to deteriorate. Within one month of starting steroid therapy, the patient developed oliguria, and her serum creatinine levels soared to 583.44 μmol/L, necessitating hemodialysis. Nevertheless, the patient's response to treatment was favorable, and she could eventually discontinue hemodialysis after 21 months, as her serum creatinine level decreased to 251.06 μmol/L.
This case highlights the importance of considering GPA as a potential differential diagnosis when encountering a solitary renal mass, even though it is exceedingly rare. Early identification and appropriate management are crucial in mitigating the impact of this potentially life-threatening condition.
Source:
Higashihara, M., Kawamura, T., Miyazaki, Y., Yokoo, T., & Joh, K. (2023). Granulomatosis with polyangiitis presenting as a solitary renal mass: a case report. In BMC Nephrology (Vol. 24, Issue 1). Springer Science and Business Media LLC. https://doi.org/10.1186/s12882-023-03276-1