Okay, let's tackle this question. The patient is a 45-year-old woman with mononeuritis multiplex, a history of bronchial asthma and allergic rhinitis, cutaneous purpura, and eosinophilia. Mononeuritis multiplex is a sign of vasculitis, so I need to think about conditions that cause both vasculitis and these other symptoms.

Eosinophilia is a key clue here. That makes me think of eosinophilic disorders. Churg-Strauss syndrome (now called eosinophilic granulomatosis with polyangiitis, EGPA) comes to mind because it's a type of vasculitis that affects small and medium vessels. It's associated with asthma, allergic rhinitis, eosinophilia, and can cause peripheral neuropathy like mononeuritis multiplex. The cutaneous purpura could be due to vasculitic lesions.

Other possibilities might include other vasculitides like granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA), but those don't typically have the asthma and eosinophilia. GPA is more associated with upper respiratory tract granulomas and ANCA positivity. MPA is similar but without granulomas. Behçet's disease is another vasculitis but presents with oral ulcers, uveitis, and skin lesions, not really asthma or eosinophilia.

So the correct answer should be EGPA. The options probably include EGPA, GPA, MPA, and Behçet's. The presence of asthma, allergic rhinitis, and eosinophilia points to EGPA. The clinical pearl here is that EGPA is part of the vasculitis classification and is characterized by asthma, eosinophilia, and systemic vasculitis. The mononeuritis multiplex is a common presentation. Students should remember the triad of asthma, eosinophilia, and vasculitis in EGPA.

**Core Concept**
Mononeuritis multiplex in a patient with asthma, allergic rhinitis, eosinophilia, and purpura suggests a systemic vasculitis. *Eosinophilic granulomatosis with polyangiitis (EGPA)*, formerly Churg-Strauss syndrome, is a key differential diagnosis in such cases. It is characterized by asthma, eosinophilia, and necrotizing vasculitis affecting small and medium vessels.

**Why the Correct Answer is Right**
EGPA is a systemic vasculitis associated with a triad of asthma, eosinophilia, and systemic necrotizing vasculitis. The patient’s mononeuritis multiplex (a hallmark of vasculitic neuropathy), allergic rhinitis, and cutaneous purpura (from vasculitis) align with EGPA. Eosinophils infiltrate tissues and release cytotoxic mediators, contributing to nerve damage and vasculitic lesions. The presence of asthma and allergic rhinitis further supports EGPA over other vasculitides.

**Why Each Wrong Option is Incorrect**
**Option A:** *Granulomatosis with polyangiitis (GPA)* is characterized by upper/lower respiratory tract granulomas and renal involvement but lacks asthma and eosinophilia.
**Option B:** *Microscopic polyangiitis (MPA)* involves small-vessel vasculitis with

✓ Correct Answer: C. Churg strauss syndrome