Acute Renal Failure Revealing Primary Renal Lymphoma With Bone Involvement: A Rare Case.

Primary renal diffuse large B-cell lymphoma is rare, and its presentation with acute kidney injury (AKI) due to bilateral renal infiltration, occasionally associated with bone involvement, is exceptionally uncommon. We report the case of a 46-year-old man with a history of low back pain, previously misdiagnosed as lumbosacral radiculopathy, who was admitted for severe AKI. Imaging revealed bilaterally enlarged kidneys with multiple hypodense parenchymal lesions, without evidence of extrarenal disease. Renal biopsy confirmed diffuse large B-cell lymphoma, and further evaluation revealed secondary bone involvement. The patient was promptly referred for chemotherapy to preserve renal function. This case highlights the diagnostic challenges of primary renal lymphoma (PRL), as its clinical and radiological presentation is nonspecific; the disease should be suspected in atypical AKI, emphasizing that early histological diagnosis is crucial to ensure timely and effective management.