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Abstract: PO1519

Unmasking a Case of Membranous-Like Glomerulopathy with Masked IgG-κ Deposits

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Ice, Alissa, Louisiana State University Health Sciences Center, Baton Rouge, Louisiana, United States
  • Barefield, Darren W., Louisiana State University Health Sciences Center, Baton Rouge, Louisiana, United States
Introduction

Membranous-like glomerulopathy with masked IgG-κ deposits (MGMID) is a recently described, exceedingly uncommon entity of glomerular immune-complex deposition requiring antigen retrieval on formalin-fixed paraffin-embedded tissue. We report a rare case of MGMID in a young female with newly diagnosed APLA.

Case Description

An 18 year old female with no medical history presented with left leg swelling. Vital signs were normal and an enlarged, discolored left lower extremity was appreciated on exam. Initial laboratory results were remarkable for Cr 0.78 mg/dL, albumin 2.3 g/dL, platelets 128,000/µL, PTT 87.1 s, INR 1.02, and hematuria and proteinuria on UA. Imaging demonstrated an extensive acute DVT. Additional studies revealed positive APLA, unremarkable bone marrow and flow cytometry analyzes, and negative autoimmune panel. Hepatitis panel, ANCA, anti-PLA2R, serum free light chains, and serum and urine immunoelectrophoreses were normal. Furthermore, she was found to have 7.2 g of protein on 24 hour collection and biopsy results consistent with MGMID. She was discharged on a prednisone taper and losartan and later initiated on tacrolimus with stable renal function and improved proteinuria after six months.

Discussion

MGMID was first described in 2014 by Larsen et al found predominantly amongst young female patients with autoimmune phenomena with variable clinical progression regardless of the treatment. Similar to this case, subepithelial and mesangial deposits [A], predominant C3 on IF [B], SAP positivity [C], and IgG-κ deposits [D] appear to be characteristic [see figure]. Given these findings in the absence of the antigen-retrieval step, pathology misclassifcation as infection-associated glomerulonephrtis, membranous nephropathy, or C3 glomerulonehritis can significantly impact prognosis and treatment. Therefore, it is important to consider this additional step in pathology analysis in certain clinical presentations.

Figure 1: Pathology