Clinicopathological features of idiopathic membranous nephropathy combined with IgA nephropathy: a retrospective analysis of 9 cases

BACKGROUND The concomitant presence of idiopathic membranous nephropathy and IgA nephropathy is rare. Here, we report 9 cases of phospholipase-A2-receptor (PLA2R) positive idiopathic membranous nephritis combined with IgA nephropathy, while reviewing publications regarding the pathological characteristics of this glomerolonephritis complication. CASE PRESENTATION Nine cases of renal biopsy tissues were retrospectively reviewed, including the clinicopathological features, the results of the immunofluorescence assays, and the electron microscopic examination. The patients mainly presented proteinuria and microscopic hematuria, and the serum anti-PLA2R was detected as positive in all of the patients. Histologically, a wide thickening of the glomerular basement membrane was observed in each of the 9 cases. Additionally, there existed mild hyperplasia in the mesangial cell and the matrix of the mesangial area. Immunofluorescence assays showed prominent glomerular granular staining on the glomerular capillary loops for IgG (++/+++), IgG4 (++/++++), and PLA2R (+/++). In addition, moderate IgA positive stains were focally or sparsely limited to the mesangial areas. Electron microscopy revealed subepithelial and mesangial electron-dense deposits. CONCLUSIONS The results from the case analyses indicated that idiopathic membranous nephropathy combined with IgA nephropathy possess the clinicopathological features found in both components. It is suggested that serum anti-PLA2R and tissue PLA2R are important biomarkers that can assist in the diagnosis of idiopathic membranous nephropathy associated with IgA nephropathy.