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Conference Proceeding

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Publication Title

Archives of Pathology & Laboratory Medicine


Context: Immunoglobulin M (IgM) glomerulopathy usually presents as drug-resistant nephrotic syndrome and is characterized by diffuse effacement of foot processes and scattered mesangial IgM deposits, which is considered within the spectrum of minimal change disease and primary focal segmental glomerulosclerosis. However, IgM-dominant immune complex–mediated glomerulonephritis (IgM-ICMGN) is a rare renal entity and usually characterized by a membranoproliferative pattern with light microscopy; dominant IgM staining by immunofluorescent staining; and subendothelial, mesangial, and occasional subepithelial deposits by electron microscopy.

Design: We report our experience of 5 IgM-ICMGN cases with their pathologic phenotypes and clinical scenarios.

Results: Patient ages ranged from 47 to 87 with 3 women (F) and 2 men (M) (Table). Four of 5 patients had drug-induced autoimmune phenomenon (hydralazine-induced positive ANCA and ANA), except case 3 with recent COVID-19 infection. All patients had renal dysfunction and some proteinuria. Pathologic features of 5 cases all showed a typical membranoproliferative pattern of glomerulonephritis with dominant IgM deposits and dominant subendothelial deposits. The major differential diagnosis for the above changes included IgM-ICMGN, chronic thrombotic microangiopathy, and cryoglobulinemic glomerulopathy. Ultrastructural findings did not support the latter 2 entities and the serum cryoglobulin was negative in all, therefore IgM-ICMGN was favored.

Conclusions: Drug-induced autoimmune phenomenon can be seen in IgM-ICMGN, which should be classified as a subtype of membranoproliferative glomerulonephritis (type 1 or type 3 depending on the locations of deposits)





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College of American Pathologists 2023 Annual Meeting CAP23, October 7-10, 2023, Chicago, IL



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