Eosinophilic infiltrates of the gastrointestinal tract

Eosinophilic infiltration, localised or diffuse, of the gastrointestinal tract cannot be regarded as a definitive diagnosis; neither can a classification of disease, in which this is a feature, be founded on the degree or site of such infiltration. Eosinophilia is merely a manifestation of inflammation, often with an allergic basis, and accompanies a number of well defined clinicopathological conditions, some of which have a known cause-for example, parasitic infestation-but most of which do not. Eosinophils are normally present in the lamina propria of the gut mucosa, and there is no generally agreed number which is pathological. Groups of eosinophils are not normally found in the submucosa, muscle coat, or serosa. The common diagnostic dilemma, however, is not "are there increased numbers of eosinophils present in this lesion?" but rather, "what is the pathological importance of the eosinophilic infiltrate in this lesion?" An eosinophilic infiltrate in the bowel may either point to the nature of the underlying condition or may obscure it, and the confusing studies on the subject reflect the diagnostic, conceptual, and terminological difficulties entailed. The name of eosinophilic granuloma has been applied to at least two primary gut conditions. Although the authors who originally described these conditions were careful to distinguish them clinically and pathologically from eosinophilic granuloma of bone (histiocytosis X), the continued use of the term has led to confusion. This confusion is exacerbated by the fact that the two gut entities so named are very different and can clearly be separated from each other pathologically, and to some extent, clinically. These