Table 6.

Brief summary of renal biopsy findings in Staphylococcus infection–associated GN and differential diagnostic entities

DiseaseLight MicroscopyDirect ImmunofluorescenceElectron Microscopy
Staphylococcus infection–associated GNEndocapillary hypercellularity is significantly more common than IgAN. Crescents are more frequent but much less common than ANCA, FSGS pattern is not seenVariable 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 nephropathyEndocapillary hypercellularity is less frequent than in SAGN. Crescents are less common, and segmental. FSGS pattern is significantly more common than SAGNStrong IgA, mild-to-moderate C3Mesangial 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 crescentsStrong IgA, mild or moderate C3Mesangial deposits most common. Few small subendothelial deposits
ANCA vasculitisCrescents 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 glomeruliMild IgA, no accompanying C3No or few mesangial electron dense immune-type deposits.
Post-streptococcal GNEndocapillary hypercellularity common and usually global and diffuse, crescents are uncommonStrong C3 with lumpy-bumpy coarse staining. IgA negative. IgG can be presentSubepithelial humps numerous
C3 glomerulopathy (excluding dense-deposit disease)Mesangial and endocapillary hypercellularity is common. Crescents are uncommonStrong 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 seenMesangial and capillary wall deposits. Humps may be seen, but are not required for diagnosis
Cryoglobulinemic GNMesangioproliferative pattern common. Intracapillary inflammatory cells are monocytes, not PMNs. Hyaline thrombi may be presentWide 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 loopsMicrotubular 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.