Supplementary Material for: Recurrent Fibrillary Glomerulonephritis Secondary to Chronic Lymphocytic Leukaemia: Remission of kidney disease with Ibrutinib

Fibrillary glomerulonephritis (FGN) is a rare form of glomerular disease accounting for less than 1 percent of all renal biopsies. It is characterized by pathognomonic electron microscopic findings of fibrillar deposits in the mesangium and glomerular capillary walls. FGN was initially considered to be an idiopathic disorder. However, approximately 30 to 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. In this case report, we present a 69-year-old male who was diagnosed with CLL in 2013 he was initially managed conservatively. He developed subsequent nephrotic syndrome and renal impairment in 2016. A renal biopsy showed FGN and treatment was targeted to the CLL with bendamustine and rituximab which led to 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 he was treated with ibrutinib (a tyrosine kinase inhibitor). He achieved a significant organ response and a further sustained remission. 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 to prevent end-stage renal failure.