New-onset haematoproteinuria in a 63-year-old man with intraperitoneal lymph node enlargement.

A 63-year-old man was referred to our hospital because of renal dysfunction with haematoproteinuria. Intraperitoneal lymph node enlargement was also noted. M protein was not detected by electrophoresis of his serum and urine; however, an increase in the κ/λ ratio was detected by free light-chain assay. Percutaneous kidney biopsy was performed, and the patient was diagnosed with proliferative glomerulonephritis with monoclonal immunoglobulin deposits. Lymph node biopsy showed follicular lymphoma. Urinalysis findings improved after treatment of the lymphoma. Proliferative glomerulonephritis with monoclonal immunoglobulin deposits is rarely considered to be associated with haematological disease. We report a case of lymphoma-associated proliferative glomerulonephritis with monoclonal immunoglobulin deposits with light-chain abnormality detected by free light-chain assay, but not by electrophoresis. 2016 BMJ Publishing Group Ltd.