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Abstract: PO1501

A Case of an Elderly Woman with Membranous-Like Glomerulopathy with Masked Monoclonal IgG Deposits Whose Renal Biopsy Revealed Renal Cell Carcinoma

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Nishikawa, Sho, Fukui Daigaku Igakubu, Yoshida-gun, Fukui, Japan
  • Takahashi, Naoki, Fukui Daigaku Igakubu, Yoshida-gun, Fukui, Japan
  • Morita, Sayu, Fukui Daigaku Igakubu, Yoshida-gun, Fukui, Japan
  • Nishimori, Kazuhisa, Fukui Daigaku Igakubu, Yoshida-gun, Fukui, Japan
  • Sakashita, Sayumi, Fukui Daigaku Igakubu, Yoshida-gun, Fukui, Japan
  • Fukushima, Sachiko, Fukui Daigaku Igakubu, Yoshida-gun, Fukui, Japan
  • Kasuno, Kenji, Fukui Daigaku Igakubu, Yoshida-gun, Fukui, Japan
  • Iwano, Masayuki, Fukui Daigaku Igakubu, Yoshida-gun, Fukui, Japan
Introduction

Membranous-like glomerulopathy with masked monoclonal IgG deposits (MGMID) is a recently described form of glomerulopathy with a unique histopathology reported by Larsen et.al. The pattern is characterized by subepithelial and/or mesangial immune deposits that are “masked”, to immunoglobulin staining by routine immunofluorescence but strongly stained for IgG and kappa light chain after protease digestion. Patients with MGMID are commonly young females and have a vague history of autoimmune diseases such as low titer antinuclear antibodies.

Case Description

A 65-year-old woman was referred to our hospital with urinary protein (0.80 g/gCr) and microscopic hematuria. Serum antinuclear antibody, rheumatoid factor, and M-protein were negative and serum C3 and C4 were normal. Plain CT showed no neoplastic lesions in the kidney, and a renal biopsy was performed. Part of kidney biopsy tissue contained clear cell renal carcinoma (RCC). Light microscopy revealed increased mesangial matrix and partial thickening and double contour of the basement membrane. Immunofluorescence examination of the frozen sections was negative for IgG and C3. Electron microscopy revealed electron dense deposits in both the subepithelium and mesangium (Churg classification stage II). After proteinase digestion, paraffin-embedded sections were stained again, and IgG and kappa light chain were strongly positive in granular pattern along the basement membrane (IgG subclass: IgG1>IgG4). Staining for anti-PLA2r/THSD7A antibody was negative, and staining for anti-serum amyloid P antibody was positive. Based on the above, this patient was diagnosed as MGMID. Subsequently, she underwent a partial nephrectomy for RCC, and her urinary protein decreased significantly.

Discussion

Although most patients with MGMID are young women (<40 years), this patient was an elderly woman with RCC. IgA nephropathy and membranous nephropathy have been reported as glomerular lesions associated with RCC. In this case, the proteinuria decreased after RCC resection, suggesting that RCC may be related to the development of MGMID in elderly patients, although the details are unknown. This is the first case of MGMID in Japan.