PMC9876708_01
Skin lesion. a: Purpura on the lower leg. b: Light microscopy: Neutrophils with nuclear debris and eosinophils (arrow) are seen surrounding blood vessels in the subcutaneous tissue (Hematoxylin and Eosin staining). c: Immunofluorescence microscopy: Blood vessels showed positivity for IgA (arrow).
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Non-blanching palpable purpura was noted in scattered patches on the lower limbs and left abdomen (Fig. 1a). Neutrophils with nuclear debris and eosinophils were seen surrounding blood vessels in the subcutaneous tissue, and leukocytoplastic vasculitis was diagnosed (Fig. 1b). In addition, immunofluorescence microscopy showed IgA, C3 and fibrinogen depositions in the blood vessels (Fig. 1c).
Kidney lesion. Microscopy findings of the kidney biopsy specimen. a: Light microscopy: Almost all glomeruli displayed endocapillary glomerulonephritis that was characterized by endothelial cell swelling (arrow), resulting in the obstruction and/or narrowing of the glomerular cavity; periodic acid-Schiff staining. b: Light microscopy: Double-contour appearance and thickening of the glomerular basement membrane (arrow) (periodic acid-methenamine silver staining). c: Light microscopy: CD68-positive cells (arrow) were seen in the glomeruli (CD68 staining). d: Immunofluorescence microscopy: Glomeruli showed mild positivity for IgA (green area, arrow). e: Electron microscopy: Endothelial cells were swollen, and subendothelial edema was seen (black arrow); electron-dense deposits (white arrow) were found in the subendothelial space. f: Electron microscopy: electron-dense deposits (white arrow) were found in the paramesangial area.
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Almost all glomeruli displayed endothelial damage-dominant nephritis, which was characterized by endothelial cell swelling with subendothelial edema (resulting in obstruction and/or narrowing of the glomerular cavity) (Fig. 2a) and a double-contour appearance and thickening of the glomerular basement membrane (Fig. 2b); however, neither thrombosis nor spike formation was observed. CD68-positive cells (related to the development of IgA vasculitis) were seen in the glomeruli (Fig. 2c). Immunofluorescence microscopy showed that the glomeruli were mildly positive for IgA (Fig. 2d), positive for IgA1, and weakly positive for C3; however, they were negative for IgG and IgM. Small amounts of electron-dense deposits were noted in the subendothelial space and paramesangial area, and moderate foot process effacement was seen (Fig. 2e, f).
Clinical course. MTX: methotrexate, TCZ: tocilizumab, PSL: prednisolone, mPSL: methylprednisolone
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With continued monotherapy with tocilizumab, the RA disease activity subsided, and proteinuria is negative as of the most recent examination (at 20 months) (Fig. 3).