Churg-Strauss syndrome (CSS) is a systemic small vessel vasculitis involving lungs, skin, heart, gastrointestinal tract and peripheral nerves. We report the case of a 36-year-old woman with a necrotic lesion on the left foot of two months duration, associated with hypereosinophilia, patchy lung infiltrates, cardiac damage and a mononeuritis. The personal history was remarkable only for an asthma, treated with Montelukast, a leukotriene receptor antagonist (LRA). Clinical symptoms, laboratory exams and instrumental examinations led us to the diagnosis of CSS. In recent years several studies have reported the possible relationship between use of leukotriene receptor antagonist (LRA) and CSS expression. We report this case to underline the possible relationship between LRA and CSS and its etiopathogenetic mechanism.