Clinical meaning
Eosinophilic granulomatosis with polyangiitis (EGPA), formerly Churg-Strauss syndrome, is an ANCA-associated small-vessel vasculitis characterized by eosinophilic infiltration, granuloma formation, and necrotizing vasculitis. It progresses through three phases: prodromal (allergic rhinitis, nasal polyps, adult-onset asthma), eosinophilic (peripheral eosinophilia with tissue infiltration of lungs, GI tract, heart), and vasculitic (systemic vasculitis affecting skin, nerves, kidneys, heart). Cardiac involvement (eosinophilic myocarditis, coronary arteritis) is the leading cause of death.
Exam relevance
Risk factors: - Adult-onset asthma (present in nearly all cases) - Allergic rhinitis and nasal polyposis - History of allergic disease or atopy - Use of leukotriene receptor antagonists (montelukast)—may unmask rather than cause EGPA - Age 40–60 years - No clear gender predominance
Diagnostics: - Peripheral eosinophilia > 10% or > 1,500/μL (hallmark finding) - ANCA testing: p-ANCA/anti-MPO positive in ~40% of cases - Tissue biopsy showing eosinophilic infiltration, granulomas, and necrotizing vasculitis - Chest X-ray/CT: transient, patchy, migratory pulmonary infiltrates - Echocardiogram for eosinophilic myocarditis assessment - Nerve conduction studies for mononeuritis multiplex - Urinalysis for hematuria/proteinuria (renal involvement)