Eosinophilic Gastrointestinal Disorders Pathology

Abstract

Eosinophilic gastrointestinal disorders (EGID) are characterized pathologically by excess eosinophils in mucosal biopsies of one or multiple sites in the gastrointestinal (GI) tract, simultaneously or sequentially. Eosinophilic esophagitis (EoE) is the best characterized EGID, and in most patients it is an abnormal immune-mediated response to food antigens. Current recommendations for diagnosis include signs and symptoms of esophageal dysfunction that do not respond to proton-pump inhibitor therapy, and esophageal biopsies that exhibit at least 15 intraepithelial eosinophils in at least one high power field (HPF). Therapy consists of swallowed glucocorticoids or dietary elimination. Eosinophilic gastritis (EG) is the second most common form of EGID, but like all forms of EGID except EoE consensus recommendations for either clinical or pathological diagnosis do not exist. EG may be associated clinically with peripheral blood eosinophilia, hypoalbuminemia, and anemia, and pathologically with marked expansion of lamina propria by dense eosinophilic infiltrates. Eosinophilic enteritis (EE) may be subdivided into eosinophilic duodenitis, eosinophilic jejunitis, and eosinophilic ileitis. Most investigators believe that EE rarely, if ever, exists as a solitary form of EGID and is encountered only in patients who have at least one other affected portion of the GI tract. Eosinophilic colitis (EC) is perhaps the most enigmatic EGID. Distinction of EC from inflammatory bowel disease may be problematic especially in children. Multiple possible etiologies for EGID include hypereosinophilic syndrome, drug reactions, etc. Currently, the only etiology that can be identified histologically is parasitic infestation, if a portion of an invasive parasite is found in mucosal biopsies. This review will provide guidelines for the pathologic diagnosis of the various forms of EGID.

Keywords: allergy; colitis; esophagitis; genome; inflammatory bowel disease.

Figure 1

Numerous eosinophils (arrows) are found in the epithelium of this esophageal biopsy. The basal zone is markedly expanded (bar). Lamina propria fibers appear thickened near the epithelium (black asterisk), but not at the deep margin (white asterisk). Eosinophils are also present in the lamina propria (shaded arrows).

Figure 2

Extracellular eosinophil granules are seen (arrows). Intercellular bridges (shaded arrows) are visible in the dilated intercellular spaces.

Figure 3

The lamina propria of this section of gastric mucosa is almost entirely occupied by sheets of eosinophils (arrows). Numerous intraepithelial eosinophils are found in gland epithelium (arrowheads).

Figure 4

This duodenal biopsy shows few preserved short villi (asterisk), elongated crypts (bar), and numerous eosinophils in the lamina propria (arrows), muscularis mucosa (shaded arrows), and submucosa (arrowheads).

Figure 5

This view of Figure 4 illustrates blunt villi (asterisk) and confirms numerous lamina propria eosinophils (arrows).

Figure 6

A different biopsy shows numerous eosinophils in duodenal lamina propria (arrows) and crypt epithelium (shaded arrows).

Figure 7

Numerous eosinophils populate the lamina propria (arrows) in this well-oriented section of colonic mucosa and also invade crypt epithelium (arrowheads).

Figure 8

Virtually all crypts in this field of a colon biopsy display increased numbers of intraepithelial eosinophils (arrowheads).