MPO and anti-neutrophil cytoplasmic antibody-associated vasculitis: Although EGPA is a form of AAV, ANCA only exists in approximately one-third of EGPA patients, which always displays with a perinuclear labeling on immunofluorescence analysis with specificity against myeloperoxidase (MPO) [1, 6, 7].The disease course of classical EGPA is roughly divided into three phases.