PAN vs GPA (Wegener)
How to tell PAN and GPA (Wegener) apart when a board question makes them look alike.
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Pulmonary parenchymal involvement is the fastest discriminator, because GPA commonly affects lungs while PAN classically spares them.
Side by side
Medium-vessel vasculitis with neuropathy, abdominal ischemic pain, renal artery involvement, and no pulmonary parenchymal disease suggests polyarteritis nodosa.
Small-vessel vasculitis with destructive ENT disease, pulmonary nodules or hemorrhage, and glomerulonephritis suggests granulomatosis with polyangiitis.
PAN is a transmural necrotizing vasculitis of medium arteries that typically spares arterioles, venules, and capillaries.
GPA is an ANCA-associated necrotizing granulomatous small-vessel vasculitis involving respiratory tract and kidneys.
PAN is usually ANCA negative, may have hepatitis B surface antigen positivity, angiography with microaneurysms or segmental stenoses, and urinalysis without RBC casts because glomeruli are usually spared.
GPA often shows PR3-ANCA positivity, chest imaging with cavitary nodules, and urinalysis with dysmorphic RBCs or RBC casts from pauci-immune glomerulonephritis.
The trap
Both can present with constitutional symptoms and kidney dysfunction, so PAN is misdiagnosed as GPA. The resolving clue is compartment: PAN causes renovascular hypertension without glomerulonephritis, while GPA causes active urinary sediment and respiratory tract granulomatous disease.
The repair move
Next best step: define vessel size and organ pattern before immunosuppression intensity is chosen. If PAN is likely, evaluate hepatitis B status and begin high-dose glucocorticoids, adding cyclophosphamide for severe organ-threatening disease. If hepatitis B associated PAN is present, combine antiviral therapy with a shorter steroid course and consider plasma exchange in severe cases.
Try a free question
CoreA 48-year-old man has severe hypertension, abdominal pain after meals, mononeuritis multiplex, and livedo reticularis. Angiography shows renal artery microaneurysms, and urinalysis has no RBC casts. What is the most likely diagnosis?
Show answer and explanation
Answer: A. Polyarteritis nodosa. Medium-vessel ischemic disease with microaneurysms and no glomerulonephritis is classic for PAN.
Why the other choices are tempting
- B. GPA usually includes respiratory tract granulomatous disease and often glomerular urinary sediment.
- C. MPA is a small-vessel pulmonary-renal syndrome rather than medium-vessel aneurysmal disease.
- D. Takayasu involves large vessels and pulse deficits, not this medium-vessel pattern.
- E. Temporal arteritis primarily affects cranial arteries in older adults with headache and visual symptoms.
Flashcards
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What single organ-system clue most quickly separates PAN from GPA?
Pulmonary parenchymal disease favors GPA, while PAN typically spares the lungs.
Why do RBC casts argue against PAN?
RBC casts reflect glomerulonephritis, which is typical of GPA and usually absent in PAN.
Quick answers
What is the fastest way to tell PAN from GPA (Wegener)?
Pulmonary parenchymal involvement is the fastest discriminator, because GPA commonly affects lungs while PAN classically spares them.
What is the key clue for PAN?
Medium-vessel vasculitis with neuropathy, abdominal ischemic pain, renal artery involvement, and no pulmonary parenchymal disease suggests polyarteritis nodosa.
What is the key clue for GPA (Wegener)?
Small-vessel vasculitis with destructive ENT disease, pulmonary nodules or hemorrhage, and glomerulonephritis suggests granulomatosis with polyangiitis.
What is the common trap with PAN vs GPA (Wegener)?
Both can present with constitutional symptoms and kidney dysfunction, so PAN is misdiagnosed as GPA. The resolving clue is compartment: PAN causes renovascular hypertension without glomerulonephritis, while GPA causes active urinary sediment and respiratory tract granulomatous disease.