#2464 Case report of a granulomatous interstitial nephritis in chronic lymphocytic leukemia

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Abstract Background and Aims Chronic lymphocytic leukemia (CLL) is known for involving extranodal sites, but its manifestation as direct kidney infiltration leading to significant renal dysfunction and granulomatous interstitial nephritis (GIN) remains a rarity. This report underscores the diagnostic challenges and highlights the necessity of considering CLL as an etiology in patients with renal dysfunction and a history of CLL, providing insights into a unique clinical scenario of CLL-related GIN. Method We present a detailed case study of a patient. Results A 70-year-old patient with a history of Parkinson's disease, untreated B-cell CLL, and stage 4 chronic kidney disease was admitted due to worsening renal function. At admission, creatinine levels had risen sharply to 4.76 mg/dL from 2.95 mg/dL three months prior, with a glomerular filtration rate of 13 mL/min/1.73 m² and urea levels at 31 mmol/L. Urinalysis showed non-glomerular proteinuria (0.8 g/24 h) with severe albuminuria (albumin-creatinine ratio of 62 mg/mmol). Viral serologies were negative, and no significant paraproteinemia or autoantibodies (anti-nuclear, anti-ANCA) were detected; complement levels were normal. Renal imaging techniques such as scintigraphy and echography indicated bilateral renal dysfunction without structural abnormalities, and PET-CT scans suggested indolent lymphoma. A renal biopsy revealed chronic, granulomatous tubulointerstitial nephritis without necrosis. Differential diagnoses such as sarcoidosis, tuberculosis, and drug-induced nephritis were systematically excluded, implicating CLL as the underlying cause. The diagnosis was confirmed by typical immunostaining (CD20+, CD5+, CD23+, Cycline D1−). Remarkably, post-corticotherapy, the patient's renal function returned to baseline levels. Conclusion This case report enhances the understanding of CLL's potential to cause GIN and subsequent renal failure, emphasizing the importance of considering CLL in the differential diagnosis of unexplained renal dysfunction in patients with a known history of CLL. It also illustrates the efficacy of corticotherapy in reversing renal decline in such contexts. Figure: Histopathological findings (biopsy image).

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