MPO and allergic rhinitis: EGPA is characterized by three phases: 1) a prodromal “allergic” phase with asthma, allergic rhinitis and sinusitis, 2) a subsequent variable period of up to 8–10 years with eosinophilia and pulmonary infiltrates, eosinophilic cardiomyopathy and gastrointestinal involvement, and 3) a third phase in which the features of vasculitis, as palpable purpura and glomerulonephritis, occur in association with ANCA positivity, usually with anti-myeloperoxidase (anti-MPO) specificity (1, 5, 7).