LAUSR

Abstract Based on analyses of normal human tissues, we know that the only nonhematopoietic organ showing relevant numbers of tissue-dwelling eosinophils under healthy conditions is the gastrointestinal tract. Besides these resident eosinophils, a marked accumulation of eosinophils can be seen in the digestive tract under inflammatory conditions. Of note, resident and inflammation-related eosinophils exert different functions. In this chapter we focus exclusively on three idiopathic, eosinophil-associated gastrointestinal disorders, in particular, on idiopathic eosinophilic esophagitis (EoE), idiopathic eosinophilic gastroenteritis (EGE), and idiopathic hypereosinophilic syndromes (HESs) with gastrointestinal involvement. The term “eosinophil-associated” denotes that the inflammatory response is histologically characterized by an eosinophil-predominant tissue infiltration. However, each of these conditions has different properties: EoE is definitely an esophagus-restricted disease with a benign long-term prognosis; in EGE, the inflammatory process can involve several segments of the gastrointestinal tract but, nevertheless, this chronic inflammation can also be considered clinically a benign disorder; and HESs are essentially a multisystem disorder that may involve several organ systems, including the digestive tract, and might have a fatal outcome. Each of these entities therefore requires a distinct diagnostic and therapeutic management.