Kidney Involvement in Sarcoidosis-Lymphoma Syndrome: A Report of Two Cases.

Sarcoidosis-lymphoma syndrome, first described by Henrik Brincker in 1986, is defined by the association of sarcoidosis with lymphoid neoplasms. This condition may present with sarcoidosis preceding, occurring concurrently with, or developing after the neoplasm. Its pathogenesis remains poorly understood. Kidney involvement by granulomatous interstitial nephritis is well-documented, including in cases of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), where granulomas typically occur in proximity to neoplastic infiltrates. However, no prior reports in the literature describe histologically confirmed granulomatous interstitial nephritis affecting the kidney in the absence of concurrent CLL/SLL infiltration. We report two patients with a history of CLL/SLL who presented with acute kidney injury (AKI). Kidney involvement by the underlying malignancy was initially suspected, supported by radiologic findings of extensive lymphadenopathy. Unexpectedly, renal biopsies revealed diffuse granulomatous interstitial nephritis without evidence of CLL/SLL. Based on these results, both patients received immunosuppressive and/or clone-directed therapies, leading to improved kidney function.