Churg Strauss syndrome (CSS) was first defined in 1951 as an allergic granulomatosis affecting small and medium-sized vessels The American College of Rheumatology established six criteria for its classification in 1990: asthma, peripheral eosinophilia, sinus involvement, pulmonary infiltrates, mononeuritis multiplex, and histology compatible with vasculitis The presence of 4 or more criteria yielded a sensitivity of 85% and a specificity of 99.7%. Before that, three criteria—asthma, peripheral eosinophilia, and systemic vasculitis—were needed Histological lesions include small-vessel angiitis and extravascular necrotizing granulomas, usually containing eosinophilic infiltrates Vasculitis could also be granulomatous or nongranulomatous and typically involves both arteries and veins in pulmonary and systemic vessels. The granulomas have a middle formed by necrotic eosinophils surrounded by palisading histiocytes and multinucleated giant cells.