Granulomatous Interstitial Nephritis Due to Small Lymphocytic Leukemia: A Management Conundrum

Introduction: Granulomatous interstitial nephritis (GIN) is a rare morphological variant of interstitial nephritis defined histologically by the presence of interstitial inflammation and 1 or more interstitial granulomas, with a low incidence of 0.5% -5.9% of biopsies of acute interstitial nephritis. Small lymphocytic leukemia (SLL) can cause infiltration of kidneys in 60–90% of patients, however, renal dysfunction is uncommon Case Description: We describe a 70-year-old male with history of hypertension, A. fib and BPH referred for declining renal function and hypercalcemia for 8-months, associated with weight loss and fatigue. Initial Creatinine was 3.57 mg/dL (baseline creatinine 0.57 mg/dl) and calcium level of 13 mg/dL with suppressed PTH. Patient's proteinuria was 1.2 grams per day with albuminuria of 50 mg per day. His SPEP was normal with k/l ratio of 2. Bone marrow biopsy showed small lymphocytic leukemia. Kidney biopsy showed B-cell infiltrates, few plasma cells, T cells and eosinophils and discrete noncaseating granulomas consistent with granulomatosis interstitial nephritis with Interstitial fibrosis and tubular atrophy (IFTA) of 70%. His presentation was consistent with GIN which is rarely associated with SLL. Patient was a started-on prednisone 60 Mg daily, with improvement of renal function to creatinine of 1.9 mg/dL. As soon as prednisone was discontinued, renal function worsened with creatinine increase to 3.2mg/dl, proving steroid sensitive GIN. Patient was started on Acalabrutinib for SLL along with prednisone and continued on prednisone 10mg with creatinine 1.7 to 1.9 mg/dL 14 months since presentation. Discussion: GIN is suspected to be a local hypersensitivity reaction, which would explain its adequate response to steroids with or without SLL directed chemotherapy. There are no established management guidelines for these cases. Here we highlight the possibility of using low dose prednisone following a taper as an option for this uncommon entity to stabilize renal dysfunction. Another aspect of our case is the degree of response to steroids in spite of severe IFTA which is clinically important. GIN associated with SLL is a rare manifestation with overall poor outcomes.