Table 6.
Brief summary of renal biopsy findings in Staphylococcus infection–associated GN and differential diagnostic entities
| Disease | Light Microscopy | Direct Immunofluorescence | Electron Microscopy |
|---|---|---|---|
| Staphylococcus infection–associated GN | Endocapillary hypercellularity is significantly more common than IgAN. Crescents are more frequent but much less common than ANCA, FSGS pattern is not seen | Variable intensity of IgA, usually mild to moderate IgA and bright C3. Sometimes weak to negative IgA, IgG, and C3 “pauci-immune” | Mesangial deposits most common. Few small subendothelial deposits. 31% of the cases show variable number of subepithelial humps |
| IgA nephropathy | Endocapillary hypercellularity is less frequent than in SAGN. Crescents are less common, and segmental. FSGS pattern is significantly more common than SAGN | Strong IgA, mild-to-moderate C3 | Mesangial deposits most common. Absence of subepithelial humps. Capillary wall deposits uncommon |
| Henoch-Schönlein purpura nephritis (rarely seen in adults) | Mesangial and segmental endocapillary hypercellularity seen, occasional crescents | Strong IgA, mild or moderate C3 | Mesangial deposits most common. Few small subendothelial deposits |
| ANCA vasculitis | Crescents are defining lesions. Coexistence of fibrous, fibrocellular, and active crescents is common. No endocapillary hypercellularity. Necrotizing arterial lesions may be present (not seen in SAGN) | “pauci-immune” | Few-to-absent immune complex deposits |
| Incidental mild IgA deposits (often in chronic liver disease) | Unremarkable glomeruli | Mild IgA, no accompanying C3 | No or few mesangial electron dense immune-type deposits. |
| Post-streptococcal GN | Endocapillary hypercellularity common and usually global and diffuse, crescents are uncommon | Strong C3 with lumpy-bumpy coarse staining. IgA negative. IgG can be present | Subepithelial humps numerous |
| C3 glomerulopathy (excluding dense-deposit disease) | Mesangial and endocapillary hypercellularity is common. Crescents are uncommon | Strong C3 and weak to absent IgG. IgA absent. Staining can be global or segmental mesangial and capillary wall. Lumpy-bumpy staining due to large C3 deposits may be seen | Mesangial and capillary wall deposits. Humps may be seen, but are not required for diagnosis |
| Cryoglobulinemic GN | Mesangioproliferative pattern common. Intracapillary inflammatory cells are monocytes, not PMNs. Hyaline thrombi may be present | Wide spectrum depending on the type of cryoglobulins, usually mixed IgG and IgM. IgA extremely rare. Pattern variable, usually randomly scattered in the mesangium and capillary loops | Microtubular substructure is frequently seen in type 2 cryoglobulins associated with hepatitis C and type 1 monoclonal cryoglobulins. Deposits are randomly scattered and can be intracapillary, subendothelial, and mesangial |
SAGN, Staphylococcus infection–associated GN.