Step 1 First Aid Rapid Practice Test

The main idea is that immune complex–mediated glomerulonephritis after an infection shows a granular, "lumpy-bumpy" immune deposit pattern and subepithelial immune-complex humps. After a streptococcal infection, circulating immune complexes lodge along the glomerular basement membrane and in the mesangium, producing a granular appearance on immunofluorescence with IgG, IgM, and C3. Electron microscopy then reveals subepithelial humps, which are immune complex deposits on the epithelial side of the GBM. This combination is classic for poststreptococcal glomerulonephritis. Other patterns don’t fit as well: Goodpasture disease shows a linear immunofluorescence from anti-GBM antibodies and lacks these subepithelial humps; membranoproliferative GN often has a tram-track appearance with different deposition patterns (and is not defined by subepithelial humps); IgA nephropathy has predominant IgA in the mesangium and does not present with the postinfectious granular lumpy-bumpy pattern or subepithelial humps.