A Case of M-Type Phospholipase A2 Receptor-Associated Membranous Nephropathy With IgG4-Positive Cells Infiltration in the Interstitium

A 70-year-old man was referred to our department for evaluation of nephrotic syndrome. Renal biopsy revealed membranous nephropathy (MN). Immunohistochemical analysis demonstrated IgG4-positive staining in the glomeruli and interstitial cells. The presence of serum anti-phospholipase A2 receptor (PLA2R) antibody and enhanced staining of PLA2R in the glomeruli was noted. Computed tomography unidentified the extrarenal lesions of IgG4-related disease. He was diagnosed with PLA2R-associated MN possibly complicated with IgG4 related kidney disease (IgG4-RKD). Storiform fibrosis, a typical manifestation of IgG4-RKD, was not apparent. We herein describe a case of serologically and histologically confirmed PLA2R-associated MN with IgG4+ cell infiltration into the interstitium without any signs of IgG4-RD.