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What are the pathologic features of lupus nephritis?
The Renal Pathology Society/International Society of Nephrology (RPS/ISN) classification system divides kidney biopsies into six groups based on pathologic features in the glomeruli.
The International Society of Nephrology/Renal Pathology Society Classification of Lupus Nephritis
I | Minimal mesangial lupus nephritis |
II | Mesangial proliferative lupus nephritis |
III | Focal lupus nephritis (<50% of glomeruli) |
IV | Diffuse lupus nephritis (≥50% of glomeruli) |
IV-S | Diffuse segmental lupus nephritis (<50% glomerular surface area) |
IV-G | Diffuse global lupus nephritis (≥50% glomerular surface area) |
V | Membranous lupus nephritis |
VI | Advanced sclerosing lupus nephritis |
The number of active and/or chronic (or inactive) lesions guides treatment and is important in determining the patient’s long-term kidney prognosis. Common active and chronic lesions in patients with lupus nephritis are listed below.
Active and Chronic Histologic Lesions in Patients With Systemic Lupus Erythematosus
Active lesions
- Endocapillary hypercellularity or proliferation
- Wire loops (subendothelial deposits)
- Karyorrhexis
- Fibrinoid necrosis
- Crescents (cellular or fibrocellular)
- Rupture of glomerular basement membranes
- Hematoxyphil bodies
- Hyaline thrombi (rare)
Chronic lesions
- Glomerular sclerosis
- Adhesions
- Fibrous crescents
Immunofluorescence is characterized by the presence of glomerular deposits of immune reactants that stain for IgG (dominantly), IgA, IgM, C3, and C1q (known as the “full house” pattern).
Electron-dense deposits representing immune complexes are seen on electron microscopy in the mesangium and are found in the subepithelial and/or subendothelial locations.
The presence of tubuloreticular inclusions in the glomerular capillary endothelial cell on electron microscopy is relatively specific for lupus nephritis.