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Abstract: FR-OR51

Membranous-Like Glomerulopathy with Masked Immunoglobulin G (IgG) Kappa Deposits: A Clinicopathologic Analysis of 247 Patients

Session Information

Category: Pathology and Lab Medicine

  • 1800 Pathology and Lab Medicine


  • Caza, Tiffany, Arkana Laboratories, Little Rock, Arkansas, United States
  • Hassen, Samar, Arkana Laboratories, Little Rock, Arkansas, United States
  • Waldman, Meryl, National Institutes of Health, Bethesda, Maryland, United States
  • Andeen, Nicole K., Oregon Health & Science University, Portland, Oregon, United States
  • Larsen, Christopher Patrick, Arkana Laboratories, Little Rock, Arkansas, United States

Membranous-like glomerulopathy with masked IgG kappa deposits (MGMID) is a rare autoimmune kidney disease that disproportionately affects young women and causes proteinuria and progressive chronic kidney disease. Since discovery of serum amyloid P (SAP) as a specific biomarker, there is increased recognition and the pathologic spectrum has broadened. Here, we examine 247 patients with MGMID to characterize histopathology and outcomes.


Patients with a diagnosis of MGMID were identified from 3 institutions. Clinical and laboratory data at the time of biopsy and at follow-up were obtained. Histopathology was reviewed, including light microscopy (LM), routine and paraffin immunofluorescence (IF), electron microscopy (EM), and immunostaining for SAP.


286 kidney biopsies corresponding to 247 patients with MGMID were identified, including 278 native and 8 allografts. LM demonstrated mesangial hypercellularity in 42%, segmental sclerosis in 68%, endocapillary hypercellularity in 8%, and fibrinoid necrosis and/or crescents in 9%. Over one-third had significant tubulointerstitial fibrosis. On IF, the majority of cases had 'masked' immune deposits without IgG staining on frozen sections (76%). SAP immunostaining was positive in all cases tested. EM showed subepithelial deposits and mesangial deposits in 86%. Of patients with follow-up (n=166), 58% achieved complete or partial remission, 42% had no remission or disease progression of which 9% developed ESKD. Disease flares occurred in 16%. The majority of patients received RAAS blockade and immunosuppression varied (see table).


MGMID has multiple histopathologic patterns and variable outcomes. Further follow-up is ongoing to identify the clinical impact of different treatments on disease progression.

Clinicopathologic features of MGMID