Recurrent Fibrillary Glomerulonephritis Secondary to Chronic Lymphocytic Leukemia: Remission of Kidney Disease with Ibrutinib.

Introduction: Fibrillary glomerulonephritis (FGN) is a rare form of glomerular disease that accounts for less than 1 percent of all renal biopsies. It is characterized by pathognomonic electron microscopy findings of fibrillar deposits in the mesangium and glomerular capillary walls. FGN was initially considered to be an idiopathic disorder. However, approximately 30-50 percent of patients have a secondary cause, including a history of malignancy in up to 23% of cases. Chronic lymphocytic leukemia (CLL) is a rare cause of FGN, with limited data and poor prognosis. Case Presentation: In this report, we present the case of a 69-year-old male who was diagnosed with CLL in 2013 and was initially managed conservatively. In 2016, he developed nephrotic syndrome and renal impairment. Renal biopsy showed FGN, and treatment was targeted to the CLL with bendamustine and rituximab, which led to partial remission of nephrotic syndrome and improvement in renal function. After 3 years of clinical remission, the nephrotic syndrome relapsed, and he underwent a repeat renal biopsy confirming ongoing FGN. A bone marrow biopsy confirmed CLL relapse, and the patient was treated with ibrutinib (a tyrosine kinase inhibitor). The patient achieved a significant organ response and sustained remission. Conclusion: This case highlights the success of treating a potentially identifiable cause of FGN and highlights that even at relapse, treatment can confer benefits and help prevent end-stage renal failure.