Clinicopathologic Analysis of Membranous Glomerulonephropathy

ABSTRACT

Membranous glomerulonephropathy (MGN) is the most common primary cause of the nephrotic syndrome in adults, accounting for about 20% of the cases in most series. MGN is idiopathic in the majority of cases, however approximately 25% of adults have identifiable causes (secondary MGN). To evaluate the clinical and pathologic characteristics of MGN, we reviewed the clinical data and renal biopsies from 141 cases of MGN. The mean age of the patients at biopsy was 43 years old, but patients of all age were seen (range from 3 to 76 years of age). There were 88 males and 53 females. There were 99 idiopathic MGN cases and 42 secondary MGN cases. The associated causes of secondary MGN included hepatitis B infection (18 cases), SLE (10 cases), drugs (4 cases), post-transplantation MGN (5 cases), diabetes mellitus (4 cases), syphilis (1 case) and hepatitis B infection associated with rheumatoid arthritis. The prevalence of histologic stages by Ehrenreich and Churg was as follows. Stage I was 24 cases, stage II was 72 cases, stage III was 35 cases, and stage IV was 9 cases. All patients had proteinuria. Nephrotic syndrome was observed in 39%, edema in 73%, microscopic hematuria in 49%, gross hematuria in 28%, hypertension in 13%, and the serum creatinine level above 1.5 mg/dl was in 13%. Cases with glomerulosclerosis was observed in 45 cases with an increased percentage of glomerulosclerosis in the higher grade. Immunofluorescence (IF) examination showed predominantly granular IgG (118 cases) and C3 (84 cases) stainings along the glomerular capillary wall. In idiopathic MGN, sparse mesangial IF staining was noted up to 10% of the cases. However, mesangial IF staining in SLE was observed in 33%, hepatitis B infection in 28% and diabetes mellitus in 50%. An electron microscopic examination revealed subepithelial electron dense deposits of immune complex in all cases. The prevalence of mesangial and subendothelial electron dense deposit in idiopathic MGN was present in 19% and 6%, respectively. In SLE cases, mesangial and subendothelial deposits were observed in 78% and 56%, respectively. In hepatitis B infection, mesangial and subendothelial deposits were observed in 54% and 69%, respectively. In conclusion, immune deposits in the mesangium are scanty in idiopathic MGN, and if pronounced this should increase suspicion of underlying systemic diseases, such as SLE or other infectious diseases.