GPA vs MPA
How to tell GPA and MPA apart when a board question makes them look alike.
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Destructive ENT granulomatous disease is the quickest discriminator for GPA over MPA.
Side by side
Upper airway destructive disease with pulmonary nodules and glomerulonephritis strongly favors granulomatosis with polyangiitis.
Pulmonary capillaritis with rapidly progressive glomerulonephritis and minimal ENT involvement favors microscopic polyangiitis.
GPA is an ANCA-associated necrotizing vasculitis with granulomatous inflammation affecting small vessels.
MPA is a pauci-immune necrotizing small-vessel vasculitis without granulomatous inflammation.
GPA commonly has PR3-ANCA positivity, hematuria with RBC casts, and biopsy showing necrotizing granulomatous inflammation in respiratory tract or kidney.
MPA more often has MPO-ANCA positivity, hematuria with proteinuria, diffuse alveolar hemorrhage pattern, and biopsy showing pauci-immune necrotizing vasculitis without granulomas.
The trap
Both diseases can present with pulmonary-renal syndrome, so students over-rely on ANCA subtype alone. The resolving clue is tissue pattern: granulomatous ENT or lung lesions support GPA, while capillaritis without granulomas supports MPA.
The repair move
Next best step: treat suspected severe ANCA-associated vasculitis urgently with high-dose glucocorticoids while obtaining confirmatory tissue when feasible. Give methylprednisolone 500 to 1000 mg IV daily for 3 days for organ-threatening disease, then transition to oral prednisone about 1 mg/kg/day with rituximab or cyclophosphamide for induction. Add Pneumocystis prophylaxis and monitor renal function and hematuria closely.
Try a free question
CoreA 39-year-old woman has hemoptysis, creatinine rise, and urinalysis with RBC casts. She also has recurrent sinus ulcers and otitis. What is the most likely diagnosis?
Show answer and explanation
Answer: B. Granulomatosis with polyangiitis. Pulmonary-renal disease plus destructive ENT involvement strongly indicates granulomatosis with polyangiitis.
Why the other choices are tempting
- A. MPA can cause pulmonary-renal disease but usually lacks destructive ENT granulomatous involvement.
- C. Goodpasture lacks the chronic destructive sinonasal pattern and is anti-GBM mediated.
- D. PAN usually spares glomeruli and lungs, making this presentation unlikely.
- E. Lupus nephritis can cause renal disease but does not typically produce this ENT-cavitary vasculitic pattern.
Flashcards
Tap a card to flip it.
Which clinical feature most strongly favors GPA rather than MPA in a pulmonary-renal syndrome?
Destructive ENT disease such as chronic bloody sinusitis or saddle-nose changes favors GPA.
What ANCA pattern is classically associated with GPA?
PR3-ANCA, often with cytoplasmic staining pattern, is classically associated with GPA.
Quick answers
What is the fastest way to tell GPA from MPA?
Destructive ENT granulomatous disease is the quickest discriminator for GPA over MPA.
What is the key clue for GPA?
Upper airway destructive disease with pulmonary nodules and glomerulonephritis strongly favors granulomatosis with polyangiitis.
What is the key clue for MPA?
Pulmonary capillaritis with rapidly progressive glomerulonephritis and minimal ENT involvement favors microscopic polyangiitis.
What is the common trap with GPA vs MPA?
Both diseases can present with pulmonary-renal syndrome, so students over-rely on ANCA subtype alone. The resolving clue is tissue pattern: granulomatous ENT or lung lesions support GPA, while capillaritis without granulomas supports MPA.