Clinical meaning
Eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome) is an ANCA-associated small vessel vasculitis characterized by the triad of asthma + peripheral eosinophilia + systemic vasculitis. EGPA progresses through three phases: (1) prodromal/allergic phase (years): late-onset asthma, allergic rhinitis, sinusitis; (2) eosinophilic phase: peripheral eosinophilia with eosinophilic organ infiltration (lungs, GI, heart); (3) vasculitic phase: small vessel vasculitis with granulomatous inflammation affecting multiple organs. ANCA (usually p-ANCA/MPO) is positive in only 40-60% of EGPA patients — ANCA-positive EGPA tends to have more vasculitic features (glomerulonephritis, mononeuritis multiplex, purpura), while ANCA-negative EGPA tends to have more cardiomyopathy and eosinophilic organ infiltration. Cardiac involvement (eosinophilic myocarditis, cardiomyopathy) is the leading cause of death.
Diagnosis & workup
Diagnostics & workup: - ACR classification criteria: asthma + eosinophilia >10% + neuropathy + non-fixed pulmonary infiltrates + paranasal sinus abnormality + extravascular eosinophils on biopsy (≥4 of 6) - CBC: marked peripheral eosinophilia (often >1500/μL, may exceed 10,000/μL) - ANCA: p-ANCA/MPO positive in 40-60% - Tissue biopsy: eosinophilic infiltration, necrotizing vasculitis, extravascular granulomas - Chest CT: transient patchy infiltrates, ground-glass opacities (eosinophilic) - Cardiac evaluation: echocardiography, cardiac MRI, troponin (myocarditis is leading cause of death) - EMG/NCS: mononeuritis multiplex (75% of patients) - Urinalysis: hematuria/proteinuria if renal involvement - IgE: markedly elevated