Monoclonal B lymphocytosis and minimal change disease: a new monoclonal B-cell disorder of renal significance?

Chronic lymphocytic leukemia (CLL) may induce renal complications, which are becoming increasingly common, but in this context the occurrence of minimal change disease (MCD) remains rare. Monoclonal B lymphocytosis (MBL) is a precursor state of CLL and is currently under recognized. Since MBL is seen as a benign disorder that rarely evolves into CLL, screening for MBL is not standardized and does not require any treatment. When reviewing renal disease associated with MBL, there is very scant data in the literature and to date there is no case describing the association between MBL and MCD. Here, we describe the case of a 71-year old woman admitted for nephrotic syndrome (NS). We diagnosed a MBL. Kidney biopsy revealed MCD. Treatment with corticosteroids was introduced but no improvement was observed. Chemotherapy with rituximab and chlorambucil was thus started, leading to complete remission of both MBL and MCD. To our knowledge, this is the first description of the association of MBL and MCD. This case suggests that screening for MBL may have unexpected diagnostic and therapeutic implications in patients presenting with seemingly idiopathic NS.