Immunofluorescence microscopy revealed mesangial and capillary wall IgG staining in a global distribution (Figure 2A). The biopsy results confirmed monoclonal gammopathy of renal significance (MGRS), most likely associated with his known diagnosis of CLL. He was started on the Bruton's tyrosine kinase (BTK) inhibitor zanubrutinib 160 mg twice a day to treat his leukemia and achieved remission of his CLL and improved renal function. This evidence concerns the gene BTK and B-cell chronic lymphocytic leukemia.