An IgA1-lambda-type monoclonal immunoglobulin deposition disease associated with membranous features in a patient with chronic hepatitis C viral infection and rectal cancer.

A 61-year-old man infected with hepatitis C virus developed urinary protein. Two-dimensional electrophoresis and immunoblotting of sera revealed no monoclonal proteins. Light microscopy and immunofluorescence of a kidney biopsy specimen demonstrated bubbling appearance and formation of spikes, associated with predominantly IgA1-lambda deposition, but not IgG, along glomerular capillary walls. Electron microscopy showed electron-dense deposits without any fibrillary structure located in the glomerular basement membrane. Seven months after the kidney biopsy, the patient had a surgical operation for rectal cancer. One year later, the urinary protein was still present. The present case is the first report of an IgA1-lambda-type monoclonal immunoglobulin deposition disease associated with membranous features.