Pathogenesis and Triggering Factors

Upon activation, eosinophils release cytotoxic enzymes, e.g., eosinophil cationic protein (ECP), major basic protein (MBP), eosinophil-derived neurotoxin (EDN), and eosinophil peroxidase (EPO). Extravascular ECP (8) and MBP (9) deposits have been observed, and high levels of eosinophil cytotoxic enzymes are found in CSS patient s sera, urine, and bronchoalveolar fluids (9-11). In addition, the results of a recent study suggested that EPO released by activated eosinophils could cause oxidative tissue damage (12). Taken together, these elements incriminate eosinophil cytotoxicity in CSS development. 

Although CSS etiology remains unknown, some triggering factors have been identified or suspected, including drugs and/or environmental factors (15). First, vaccinations and desensitization were incriminated in several cases (16). We usually advise CSS patients to avoid vaccination and desensitization. Second, exposures to inhaled allergens and infections (parasitic or bacterial) were also described shortly before CSS onset (17). Third, several drugs [e.g., macrolides, 

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