Proliferative, membranous, sclerosing and crescentic patterns
Mnemonic
“Nephritic bleeds, nephrotic leaks”, then name by age and trigger:
Nephritic
- IgA nephropathy - haematuria 1 to 2 days after an upper respiratory infection (“synpharyngitic”). The commonest glomerulonephritis worldwide
- Post-streptococcal - haematuria 1 to 2 weeks after a throat infection, with low complement C3. Children
- Rapidly progressive - crescents on biopsy. Goodpasture’s, ANCA vasculitis, lupus
- Alport’s - X-linked, with deafness
Nephrotic
- Minimal change - children, normal light microscopy, foot process effacement on electron microscopy, steroid responsive
- Focal segmental glomerulosclerosis - commonest in adults, associated with HIV and obesity
- Membranous - adults, anti-PLA2R antibodies, and the pattern most associated with malignancy and with drugs
“IgA is days, post-streptococcal is weeks” is the discriminator most often tested, and the complement level settles it: low C3 in post-streptococcal, normal in IgA.
Expansion
| Pattern | Typical syndrome | Examples |
|---|---|---|
| Minimal change | Nephrotic | Children, steroid responsive |
| Focal segmental glomerulosclerosis | Nephrotic | HIV, obesity, heroin, reflux |
| Membranous | Nephrotic | Adults; anti-PLA2R, malignancy, drugs, hepatitis B |
| Membranoproliferative | Mixed | Hepatitis C, cryoglobulins, complement disorders |
| Diffuse proliferative | Nephritic | Post-streptococcal, lupus class IV |
| Mesangial proliferative | Nephritic | IgA nephropathy |
| Crescentic | Rapidly progressive | Anti-GBM, ANCA vasculitis, severe immune complex disease |
Immunofluorescence is the discriminator:
- Linear IgG along the basement membrane: anti-GBM (Goodpasture) disease
- Granular deposits: immune complex disease, such as post-streptococcal or lupus
- Pauci-immune (little or no staining): ANCA-associated vasculitis
Crescents are proliferating parietal epithelial cells and macrophages filling Bowman space. They indicate severe injury with basement membrane rupture, and their presence defines rapidly progressive glomerulonephritis, which loses renal function over days to weeks and requires immediate immunosuppression and often plasma exchange.
Electron microscopy localises deposits: subepithelial in membranous and post-streptococcal (humps), subendothelial in lupus, and mesangial in IgA nephropathy.