Lupus-like membranous nephropathy during the postpartum period expressing glomerular antigens exostosin 1/exostosin 2 and phospholipase A2 receptor: a case report

Ryoma Miyasaka; Yukihiro Wada; Kazuhiro Takeuchi; Tetsuya Abe; Ryota Uchitsubo; Sayumi Kawamura; Shun Sakurabayashi; Shokichi Naito; Togo Aoyama; Akira Shimizu; Yasuo Takeuchi

doi:10.1007/s13730-023-00848-w

Lupus-like membranous nephropathy during the postpartum period expressing glomerular antigens exostosin 1/exostosin 2 and phospholipase A2 receptor: a case report

CEN Case Rep. 2024 Jan 27. doi: 10.1007/s13730-023-00848-w. Online ahead of print.

Authors

Affiliations

¹ Department of Nephrology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0374, Japan.
² Department of Nephrology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, 252-0374, Japan. wada-y@kitasato-u.ac.jp.
³ Department of Analytic Human Pathology, Nippon Medical School, Tokyo, Japan.

PMID: 38280123
DOI: 10.1007/s13730-023-00848-w

Abstract

Recently, several target antigens of membranous nephropathy (MN), such as phospholipase A2 receptor (PLA2R) and exostosin 1/exostosin 2 (EXT1/2), have been discovered. A 30-year-old woman was referred to our hospital with nephrotic range proteinuria and microscopic hematuria. She was first noted to have proteinuria before pregnancy, and her proteinuria worsened in the postpartum period. A renal biopsy showed MN. Immunofluorescence microscopy showed IgG, IgA, IgM, C3, C4, and C1q depositions in the mesangial area and glomerular capillary walls (GCWs). Regarding the IgG subclass, IgG1 and IgG3 were detected on glomeruli. Electron microscopy showed subepithelial electron-dense deposits (EDDs). EDDs were also detected in paramesangial and subendothelial areas. The diagnosis of membranous lupus nephritis (MLN) was suspected, but she did not fulfill the criteria for systemic lupus erythematosus. Neither anti-nuclear antibody nor hypocomplementemia were detected. We further evaluated glomerular EXT1/2 expressions, which were evident on GCWs. In addition, PLA2R was also detected on GCWs, although serum antibody for PLA2R was negative. She responded to immunosuppressive therapy with decreased proteinuria. In the present case, glomerular PLA2R expression implied the possibility of primary MN. However, pathological findings with a full-house staining pattern and glomerular EXT1/2 expressions were very similar to those of lupus-associated MN. Glomerular PLA2R expression appeared not to reflect immunocomplexes of PLA2R and autoantibody when considering the results for glomerular IgG subclass and the absence of serum anti-PLA2R antibody. Collectively, it is plausible that this was a case of a relatively young postpartum female who developed latent MLN rather than primary MN.

Keywords: Exostosin 1/exostosin 2 (EXT1/2); Membranous lupus nephropathy (MLN); Membranous nephropathy (MN); Phospholipase A2 receptor (PLA2R); Primary membranous nephropathy.