Glomerulonephritis and RPGN

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Glomerulonephritis and RPGN - Practical evaluation of nephritic syndrome, complement patterns and rapidly progressive GN.

Practical orientation: GN is usually a biopsy diagnosis. In rapidly progressive presentations, do not wait passively for serology before discussing urgent biopsy and treatment.

Use first: clinical summary and algorithm.

Then: differential diagnosis, workup and management tables.

Escalate: use red flags and biopsy/urgent-care sections.

Clinical summary

GN phenotype

Inflammatory glomerular disease with hematuria, dysmorphic RBCs/RBC casts, azotemia, hypertension and variable proteinuria.

RPGN

Rapid kidney function decline over days to months; urgent diagnosis and treatment required.

Key test

Kidney biopsy plus targeted serology.

Do not delay

Severe RPGN may need empiric pulse glucocorticoids while biopsy is pending.

Algorithm

Clinical manifestations

Finding	Meaning
Dysmorphic RBCs/acanthocytes	Glomerular hematuria.
RBC casts	Strongly suggests glomerular inflammation.
Proteinuria	Often subnephrotic, but nephrotic-range proteinuria can occur.
Hypertension and reduced eGFR	Common in active GN.

Initial serologic workup

Test group	Examples
Complement	C3, C4.
Autoimmune	ANA, anti-dsDNA, ANCA with MPO/PR3, anti-GBM.
Infection	Hepatitis B/C, HIV, blood cultures if endocarditis possible.
Immune-complex / paraprotein	Cryoglobulins, RF, SPEP/IFE, serum free light chains.

Complement patterns

Complement pattern	Consider
Low complement	Lupus nephritis, infection-related GN, cryoglobulinemic GN, C3G, MPGN, endocarditis and selected monoclonal deposit diseases.
Normal complement	Pauci-immune GN, anti-GBM disease, IgA nephropathy, fibrillary GN.

Extra-renal clues

Disease	Clues
IgA vasculitis	Palpable purpura, abdominal pain, GI bleeding, arthralgia/arthritis.
SLE	Fever, rash, serositis, arthritis, neuropsychiatric disease, low complement.
ANCA vasculitis	ENT disease, pulmonary hemorrhage/nodules, purpura, neuropathy.
Anti-GBM disease	Pulmonary hemorrhage, severe crescentic GN.
Cryoglobulinemic GN	Purpura, ulcers, neuropathy, arthralgia/myalgia.
Alport syndrome	Hearing loss and ocular abnormalities.

RPGN management principles

Step	Action
Recognize	Rapid creatinine rise plus nephritic sediment.
Urgent tests	Serology and kidney biopsy.
Empiric therapy	Pulse IV methylprednisolone can be started if severe and biopsy pending.
Plasma exchange	Consider in diffuse alveolar hemorrhage and selected severe anti-GBM/ANCA presentations.
Definitive therapy	Disease-specific immunosuppression and supportive nephroprotection.

Fluid Imbalance Hematuria