Abstract: A 71yearold man presented with proteinuria and hematuria,acute kidney injury on chronic kidney disease,as well as extrarenal manifestations of cerebral infarction,anemia,monoclonal IgMκ in serum immunofixation electrophoresis,positive in cold agglutinins test without cryoglobulinemia,decreased C3 and C4.Kidney biopsy showed mild proliferative glomerulonephritis with numerous PASpositive protein thrombi intracapillary and in arterial lumen,Immunoflurerscence indicated IgM and kappa light chain staining in glomeruli and arterial lumen．Electron dense deposits were observed in the mesangial,subendothelial area and intracapillary without oranigzed ultrastructure,and severe subendothelial widening on electronmicroscopic examination.The final diagnosis was intracapillary monoclonal IgM deposits disease.