PMC9795319_01
Representative images of renal biopsy findings. Light microscopy shows diffuse dense interstitial lymphoplasmacytic infiltrate (H & E stain, x 200) without evident glomerular lesions or tubulitis. The interstitial infiltrate is composed mainly of CD20-positive B lymphocytes (x 200) with admixed CD3-positive T lymphocytes (not shown) and CD138-positive plasma cells (x 200). By immunofluorescence, the interstitial inflammatory cells are predominantly positive for IgM (left x 200) and kappa light chain (x 200), and negative for lambda light chain (x 200). There is no significant glomerular staining (IgM, right, x 400). Tubular casts are positive for both kappa and lambda light chains. Electron micrographs reveal glomerular basement membrane with a trilaminar structure and a mean of thickness within normal range (left 9280X). No immune complex or paraprotein-related deposits were seen. Rare hyaline type mesangial deposits are noted (right x 13,900). There is less than 50% podocyte foot process effacement. Endothelial cells show preserved fenestration.
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Figure1
Stains for CD138 showed occasional loose aggregates of kappa-predominant plasmacytoid cells (Figure 1). 13 glomeruli were identified, 9 of which were globally sclerotic.