Granulomatous tubulointerstitial nephritis secondary to small lymphocytic lymphoma: a case report

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BACKGROUND: Granulomatous tubulointerstitial nephritis is an uncommon cause of acute kidney injury with a broad differential diagnosis that includes drug exposure, infections, autoimmune conditions, and sarcoidosis. Although renal infiltration by small lymphocytic lymphoma/chronic lymphocytic leukaemia (SLL/CLL) is frequently observed in autopsy series, it rarely results in clinically significant renal dysfunction. Granulomatous interstitial nephritis directly related to lymphomatous infiltration is particularly rare, with only a few cases described in the literature. CASE PRESENTATION: A man in his seventh decade with indolent SLL developed rapidly progressive acute kidney injury. Extensive evaluation excluded obstructive, infectious (including tuberculosis), autoimmune, and drug-related causes, and sarcoidosis was considered unlikely in the absence of supportive clinical and laboratory findings. Immunohistochemistry and molecular techniques demonstrated a clonal B-cell population consistent with SLL, establishing the diagnosis of lymphoma-related granulomatous tubulointerstitial nephritis. Treatment with high-dose corticosteroids and acalabrutinib improved renal function, though targeted therapy was discontinued due to severe infectious complications. CONCLUSION: Granulomatous tubulointerstitial nephritis secondary to lymphomatous infiltration should be considered in the differential diagnosis of unexplained acute kidney injury in patients with indolent CLL/SLL. Immunohistochemistry is crucial for confirming B-cell infiltration. Corticosteroids and targeted therapies may lead to renal improvement but require careful monitoring given the risk of infectious complications. This case adds a rare and well-documented presentation of SLL-associated granulomatous tubulointerstitial nephritis to the current medical literature.

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