it is characterized by mesangial / endocapillary proliferative , membranoproliferative or membranous features on light microscopy , granular immunoglobulin deposits restricted to a single igg subclass and a single light chain by immunofluorescence microscopy , and immune - complex type deposits by electron microscopy [ 1 , 2 ] . to date , reports of pgnmid consist of monoclonal igg deposition of igg1 , igg2 and igg3 heavy chains , but none for monoclonal igg4 deposits [ 17 ] . on the other hand , igg4-related disease is a newly recognized disease , characterized by igg4-positive plasma cell infiltration , storiform fibrosis , and it is often accompanied with elevated serum igg4 concentrations . target organ varies such as pancreas , salivary glands , kidneys , lymph nodes and lungs . today its notion is widely known and clinical reports in number are increasing . however there has been no report of igg4-related disease complicated with pgnmid . herein , we report the first case of pgnmid with monoclonal deposits of igg4-. the patient had a right lung tumor , and partial resection of the tumor revealed fibrotic changes in the lung interstitium with heavy infiltration of igg4-positive plasma cells , without malignant change . a 62-year - old woman was admitted for suspected pneumonia and nephrotic syndrome in june 2012 . she had suffered from cough and sputum from 2 weeks prior to admission . on admission , urinalysis showed heavy proteinuria ( 4.3 g / day ) with hematuria ( 510/hpf ) . white blood cell count was 8300/l with normal distribution , hemoglobin 9.9 g / dl , hematocrit 29.1% and a platelet count of 230 000/l . serum total protein was 5.8 g / dl , albumin 2.5 g / dl , blood urea nitrogen 23.8 mg / dl , creatinine 1.56 mg / dl , alanine aminotransferase 23 u / l , aspartate aminotransferase 15 u / l , lactate dehydrogenase 172 u / l and total cholesterol 138 mg / dl . serum igg was 1255 mg / dl , igg1 746 mg / dl , igg2 446 mg / dl , igg3 86.1 mg / dl and igg4 35.9 mg / dl . iga was 250 mg / dl , igm 128 mg / dl , c3 86 mg / dl and c4 32 mg / dl . light microscopy showed 13 global scleroses , 15 cellular and 2 fibrotic crescents within 38 glomeruli , with bubbling and spike appearance of the glomerular basement membrane ( gbm ) in the functioning glomeruli ( figures  1 and 2 ) . in the tubulointerstitium , severe lymphocyte infiltration , mild tubular atrophy and interstitial fibrosis were observed ( figure  1 ) . immunofluorescence studies showed granular staining 3 +  for  heavy chain , 2 +  for -light chain and trace staining for c3 , along with the gbm , but no significant staining for -light chain or c1q . immunofluorescence staining for -heavy chain subclasses showed a dominant 3 + granular staining for igg4 , trace staining for igg2 , negative for igg1 or igg3 ( figure  3 ) . immunofluorescence staining for antibodies to m - type phospholipase a2 receptor ( pla2r ) ( sigma - aldrich , usa ) was performed . immunohistochemistry study revealed igg1 dominant and minor igg4 staining of the infiltrate plasma cells in the tubulointerstitium , and normal ratio of / light chain positive plasma cells . electron microscopy revealed granular electron - dense deposits without organized structures in the subepithelial space and in the mesangial area ( figure  4 ) . bone marrow aspiration was performed because of the presence of monoclonal immunoglobulin deposition in the glomeruli . the smears were normocellular with no morphological abnormality , and 1.8% of the cells were plasma cells . serum m - protein and urine bence - jones protein were not detected by immunofixation electrophoresis . the serum free / light chain ratio was 1.06 , which is within the normal range . by the above results , multiple myeloma or underlying plasma cell dyscrasia 1.light microscopy reveals crescentic glomerulonephritis and lymphocyte infiltration in the tubulointerstitium , and interstitial fibrosis . 2.light microscopy shows bubbling and spike appearances of the glomerular base membrane in a functioning glomeruli . periodic acid - methnamine - silver stain ( 400 and magnified ) . 
 fig . 3.immunofluorescence microscopy for igg heavy chain ,  light chain ,  light chain , c3 , igg heavy chain subclasses of igg1 , igg2 , igg3 and igg4 . it displays granular staining of igg heavy chain dominant for igg4 and  light chain along glomerular capillary walls , but no significant staining for others including  light chain ( 400 ) . 4.electron microscopy reveals granular electron - dense deposits without organized structures in the subepithelial space and in the mesangial area . light microscopy reveals crescentic glomerulonephritis and lymphocyte infiltration in the tubulointerstitium , and interstitial fibrosis . light microscopy shows bubbling and spike appearances of the glomerular base membrane in a functioning glomeruli . periodic acid - methnamine - silver stain ( 400 and magnified ) . immunofluorescence microscopy for igg heavy chain ,  light chain ,  light chain , c3 , igg heavy chain subclasses of igg1 , igg2 , igg3 and igg4 . it displays granular staining of igg heavy chain dominant for igg4 and  light chain along glomerular capillary walls , but no significant staining for others including  light chain ( 400 ) . electron microscopy reveals granular electron - dense deposits without organized structures in the subepithelial space and in the mesangial area . computed tomography of the chest revealed a tumor - like mass of 2.3 cm in diameter in the base of the right lung . microscopic examination of the section revealed fibrotic changes of the lung interstitium , proliferation of lymphocytes and plasma cells , with no malignant changes . immunohistochemical study showed positive igg4 staining in half of the proliferated plasma cells ( figure  5 ) . 5.light microscopy of the resected lung tumor shows heavy plasma cells and lymphocyte proliferation , and fibrotic changes of the interstitium . light microscopy of the resected lung tumor shows heavy plasma cells and lymphocyte proliferation , and fibrotic changes of the interstitium . immunohistochemistry microscopy shows igg4-positive plasma cells in the specimen ( b ) . from these findings , she was diagnosed with pgnmid ( membranous features ) complicated with igg4-related lung disease , according to the criteria for igg4-related disease . steroid therapy was initiated by 3 days of intravenous methyl - prednisolone of 250 mg , followed by 30 mg / day of prednisolone . following the treatment , proteinuria improved gradually , while serum creatinine level showed little change . at the 1-year follow - up , the patient was found to be well with 10 mg / day of prednisolone . the urinary protein was 0.9 g / g creatinine , serum total protein 5.8 g / dl , albumin 3.8 g / dl and creatinine 3.23 mg / dl . no abnormality in the chest x - ray was found during the follow - up period . pgnmid is a disease entity distinguished by monoclonal immunoglobulin deposition restricted to a single heavy and light chain . to date , reports for igg heavy chain was restricted to igg1 , igg2 and igg3 . in the largest series reported by nasr et al . , the most common igg subclass found in the glomeruli was igg3 . although the reason why igg3 cases are dominant is yet to be determined , in previous reports it is suggested that it may be due to the characteristics of igg3 ; it is the most positively charged subclass , has the highest molecular weight making it more size - restricted by the glomerular barrier , and is the greatest compliment - fixing subclass , that could lead to glomerulonephritis [ 1 , 2 ] . however , our case presented monoclonal igg4 deposition , which has never been reported . igg4 is the least abundant igg subclass and does not activate the classical complement pathway , which partially contradicts the previous explanation regarding igg3 deposits in pgnmid . there are several reports of membranous nephropathy ( mn ) associated with igg4-related disease , with dominant igg4 deposits in the glomeruli , but without light chain monoclonality [ 10 , 11 ] . interestingly , all of these cases lacked glomerular staining by anti - pla2r . since anti - pla2r staining of the glomeruli is a sensitive examination to determine primary mn , the reports concluded that their mn cases were not primary , but secondary to igg4-related disease [ 10 , 11 ] . in our case , anti - pla2r staining of the glomeruli was also negative , and this confirms that the pathological features of the renal biopsy are not the results of  primary membranous nephropathy. although the relationship between pgnmid and igg4-related disease is elusive , there may be common mechanisms resembling the previous reports [ 10 , 11 ] , to form both membranous type pgnmid of monoclonal igg4 deposits and igg4-related disease , simultaneously . in summary , we experienced a case of pgnmid of membranous features with monoclonal igg4- deposition , along with igg4-related disease of the lung . this is the first case of pgnmid with igg4 deposits since the first literature report , and accumulation of cases is essential for further determination of pathogenesis , clinical features and outcome .
a 62-year - old woman was admitted for nephrotic syndrome and lung tumor . 
 a renal biopsy showed membranous features of the glomeruli . 
 immunofluorescence studies revealed granular igg4- deposits along with the glomerular basement membrane . 
 electron microscopy revealed granular electron - dense deposits . 
 further study denied multiple myeloma . 
 light microscopy of the resected lung tumor revealed igg4-related lung disease with no malignancy . 
 steroid therapy induced a remission of the nephrotic syndrome , with no recurrence of the lung tumor . 
 we consider that this is the first case of a proliferative glomerulonephritis with monoclonal igg deposits of igg4 subclass , and a rare concurrence with igg4-related disease .