Background: A 42-year-old previously healthy man was referred to hospital with an 8-week history of fevers, night sweats, fatigue, and unintentional weight loss. There was no past history of medical illness or any medication use. Physical examination was unremarkable. On urinalysis, the patient had hematuria (grade 4+) and proteinuria (grade 4+). Investigations: Urine phase-contrast microscopy, full blood count, renal function tests, 24-h urine collection for protein, serum immune electrophoresis, renal biopsies, phase-contrast microscopy, serological tests for antinuclear antibodies, extractable nuclear antigens, antineutrophil cytoplasmic antibodies, hepatitis B, hepatitis C and HIV, cryoglobulin test, complement testing, flow cytometry of the peripheral blood, and bone marrow biopsy. Diagnosis: Monoclonal gammopathy and a glomerulopathy, with microtubular deposits, associated with chronic lymphocytic leukemia. Management: Treatment with prednisone and cyclophosphamide did not improve proteinuria, although lymphocyte count returned to normal. The patient did not tolerate high-dose cyclophosphamide and was started on rituximab. His proteinuria completely resolved and there was complete disappearance of the microtubules.