Monoclonal immunoglobulinemia, also known as uncharacterized monoclonal immunoglobulinopathy or asymptomatic plasma cell disease. It is generally defined as an abnormal proliferation of plasma cells with an abnormal immunoglobulin (M protein) component in the serum without evidence of myeloma, macroglobulinemia, or other plasma cell disorders. The main manifestation of renal involvement is glomerulonephritis. Patients often feel fatigue, loss of appetite, wasting, anemia, edema, hypertension, and proteinuria, and those with large amounts of proteinuria may develop nephrotic syndrome, and most have varying degrees of renal dysfunction. Most of the renal pathology showed mild or focal proliferative glomerulonephritis on light microscopy. Individual severe cases may show heavy, diffuse hyperplasia of endothelial cells and thylakoid cells with infiltration of neutrophils and macrophages, and also reported as membrane proliferative, membranous and microscopic lesions. Immunofluorescence examination shows monoclonal immunoglobulin deposition in the glomerulus, specific antiserum testing shows glomerular deposits composed of circulating M proteins, electron-dense deposits in the endothelial cells and subepithelial cells within the membrane on electron microscopy, or alterations of microscopic glomerular lesions only.