• Dr. Vincenzo L'Imperio

MGMID or monotypic SAP-associated MN? Mass spectrometry changing the way we think renal pathology


Membranous-like glomerulopathy with masked IgG kappa deposits (MGMID) is a recently described entity characterized by subepithelial/mesangial immune deposits that are “masked” and requires pronase digestion on FFPE tissue to be detected.

Take home messages

- The disease mainly affects young females with nephrotic syndrome and clinical evidences of autoimmune disorders (eg. low titre ANA)

- Mass spectrometry identified serum amyloid protein (SAP) as over-expressed in glomeruli from biopsies with MGMID diagnosis but not from other forms of MN (eg. PLA2R/THSD7A)

- SAP staining was positive in all the cases of MGMID and in 4 cases of MN with IgG kappa deposits without masking features

- Co-localization studies demonstrated overlap of IgG and SAP staining

- No autoantibodies directed against SAP were found in blood sampleS of these patients by ELISA

- SAP is a sensitive and specific marker for MN with masked/unmasked IgG kappa deposits but its role in the pathogenesis of the disease requires further studies to be fully elucidated


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Sito della Scuola di Anatomia Patologica

dell'Università degli Studi di Milano-Bicocca

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