Eosinophilic granulomatosis with polyangiitis (EGPA), aka Churg–Strauss, loves showing up on exams as the “asthma + eosinophils + vasculitis” disease. If you can recognize the pattern quickly, you’ll pick up easy points on pulmonary, rheum, neuro, and renal questions.
The mnemonic: “A-E-G-P-A” = Asthma + Eosinophils + Granulomas + Purpura + ANCA
Think: EGPA is literally A-E-G-P-A.
| Letter | Hook | What to remember (USMLE-high yield) |
|---|---|---|
| A | Asthma | New or worsening adult-onset asthma is a major clue (often precedes vasculitis). |
| E | Eosinophils | Peripheral eosinophilia and tissue eosinophils → eosinophilic pneumonia-like picture. |
| G | Granulomas | Necrotizing granulomatous inflammation (small–medium vessels) in lungs. |
| P | Purpura / Peripheral neuropathy | Palpable purpura + mononeuritis multiplex (foot drop/wrist drop). |
| A | ANCA | Often p-ANCA (MPO-ANCA) positive (not always). |
One-liner: EGPA = adult-onset asthma + eosinophilia + necrotizing granulomatous vasculitis (small/medium vessels), often p-ANCA, with lung + skin + nerve involvement.
Visual memory device (shareable): “The Wheezing Eosinophil with Purple Socks”
Picture this:
- A person wheezing (asthma)
- Surrounded by eosinophils (big red granules everywhere)
- Wearing purple socks (palpable purpura)
- One sock is slipping off (foot drop = mononeuritis multiplex)
- Holding an “MPO” bottle (p-ANCA/MPO association)
If the stem gives you asthma + eosinophils and then suddenly adds neuropathy or purpura, your brain should yell: EGPA.
How it presents (what Step stems actually say)
Pulmonary clues
- Asthma (often severe, adult onset)
- Migratory pulmonary infiltrates (can resemble eosinophilic pneumonia)
- Sinusitis / allergic rhinitis (upper airway involvement is common)
Systemic vasculitis clues
- Palpable purpura
- Mononeuritis multiplex (high yield)
- Constitutional symptoms: fever, weight loss, malaise
Cardiac is a sneaky favorite
- Eosinophilic myocarditis can occur and is a major cause of morbidity/mortality (if the question mentions chest pain, arrhythmia, or heart failure in this context—perk up).
Step 1 pathology snapshot (the “triad” you should recall)
EGPA classically combines:
- Asthma
- Eosinophilia
- Necrotizing vasculitis with granulomas
On histology descriptions, expect language like:
- Small-to-medium vessel vasculitis
- Eosinophil-rich inflammation
- Necrotizing granulomas (often in lungs)
Differentiation table: don’t confuse your ANCA vasculitides
| Disease | ANCA association | Key distinguishing feature |
|---|---|---|
| EGPA (Churg–Strauss) | p-ANCA (MPO) sometimes | Asthma + eosinophilia + neuropathy/purpura |
| GPA (Wegener) | c-ANCA (PR3) | ENT + lung cavitary nodules + crescentic GN |
| Microscopic polyangiitis | p-ANCA (MPO) | No granulomas, prominent renal + pulmonary capillaritis |
Fast rule: If there’s asthma, it’s not GPA/MPA until proven otherwise—think EGPA.
Testing + diagnosis (what they might ask)
- CBC: eosinophilia
- ANCA: often MPO-ANCA (p-ANCA), but can be negative
- Imaging: transient/migratory infiltrates
- Definitive: biopsy showing eosinophil-rich necrotizing granulomatous vasculitis (if they give pathology)
Treatment (high yield, exam-friendly)
- Glucocorticoids are first-line for most
- Add immunosuppressants (e.g., cyclophosphamide, rituximab) for severe organ involvement
- Anti–IL-5 therapy (mepolizumab) can be used in EGPA due to eosinophil-driven disease (nice modern detail for Step 2-style management questions)
Rapid-fire recall (what to say in 5 seconds)
EGPA = asthma + eosinophilia + necrotizing granulomatous small/medium-vessel vasculitis, often p-ANCA, with pulmonary infiltrates + purpura + mononeuritis multiplex.