Polyarteritis nodosa vs Microscopic polyangiitis
How to tell Polyarteritis nodosa and Microscopic polyangiitis apart when a board question makes them look alike.
Polyarteritis nodosa is medium-vessel disease that classically spares lungs; microscopic polyangiitis is small-vessel pulmonary-renal disease.
Side by side
Medium-vessel necrotizing vasculitis with renal artery disease, abdominal pain, neuropathy, hepatitis B association, and lung sparing.
Small-vessel pauci-immune vasculitis with pulmonary-renal syndrome, palpable purpura, and p-ANCA/MPO association.
Segmental inflammation of medium arteries causes aneurysms, infarcts, and ischemic organ symptoms.
Small-vessel capillaritis and glomerulonephritis cause alveolar hemorrhage and rapidly progressive glomerulonephritis.
Renal microaneurysms, hypertension from renal artery involvement, hepatitis B, and no pulmonary hemorrhage point polyarteritis nodosa.
Hematuria with RBC casts, pulmonary hemorrhage, p-ANCA/MPO, and pauci-immune biopsy point microscopic polyangiitis.
The trap
Kidney disease occurs in both, but polyarteritis nodosa hits renal arteries while microscopic polyangiitis hits glomeruli.
Watch it explained
The repair move
For systemic vasculitis with kidney involvement, do three checks before naming the disease: (1) vessel size (medium-vessel renal artery branches in PAN versus small-vessel glomerular capillaries in MPA); (2) lung involvement (PAN classically spares lungs; MPA has alveolar capillaritis with hemoptysis); (3) ANCA and hepatitis B status (PAN is usually ANCA-negative and may associate with hepatitis B; MPA is p-ANCA/MPO-positive). Confirm PAN with mesenteric or renal angiography showing microaneurysms; confirm MPA with renal biopsy showing pauci-immune necrotizing glomerulonephritis.
Try a free question
CoreA patient has systemic medium-vessel vasculitis with abdominal pain, neuropathy, renal artery involvement, hepatitis B association, and no pulmonary capillaritis. ANCA testing is negative. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Polyarteritis nodosa. PAN is medium-vessel necrotizing vasculitis associated with hepatitis B, renal artery disease, neuropathy, and relative lung sparing.
Why the other choices are tempting
- B. MPA is small-vessel p-ANCA vasculitis with glomerulonephritis and pulmonary hemorrhage possible.
- C. GPA has ENT/lung/kidney granulomatous disease and c-ANCA association.
- D. Takayasu is large-vessel vasculitis in young women.
- E. Buerger disease is tobacco-associated distal extremity ischemia.
Flashcards
Tap a card to flip it.
What is the fastest separator for Polyarteritis nodosa vs Microscopic polyangiitis?
Polyarteritis nodosa is medium-vessel disease that classically spares lungs; microscopic polyangiitis is small-vessel pulmonary-renal disease.
What clue should make you choose Polyarteritis nodosa?
Medium-vessel necrotizing vasculitis with renal artery disease, abdominal pain, neuropathy, hepatitis B association, and lung sparing.
Quick answers
What is the fastest way to tell Polyarteritis nodosa from Microscopic polyangiitis?
Polyarteritis nodosa is medium-vessel disease that classically spares lungs; microscopic polyangiitis is small-vessel pulmonary-renal disease.
What is the key clue for Polyarteritis nodosa?
Medium-vessel necrotizing vasculitis with renal artery disease, abdominal pain, neuropathy, hepatitis B association, and lung sparing.
What is the key clue for Microscopic polyangiitis?
Small-vessel pauci-immune vasculitis with pulmonary-renal syndrome, palpable purpura, and p-ANCA/MPO association.
What is the common trap with Polyarteritis nodosa vs Microscopic polyangiitis?
Kidney disease occurs in both, but polyarteritis nodosa hits renal arteries while microscopic polyangiitis hits glomeruli.