MPO and eosinophilic granulomatosis with polyangiitis: Eosinophilic granulomatosis with polyangiitis, formerly known as Churg Strauss syndrome, is an ANCA-associated primary systemic vasculitis (usually against myeloperoxidase: p-ANCA) of the small-to-medium sized vessels that presents with asthma, paranasal sinus abnormalities, non-fixed pulmonary infiltrates, blood eosinophilia and tissue eosinophilic invasion.