Eosinophilic Gastroenteritis

Clinicopathologic criteria for diagnosis :1.Presence of gastrointestinal symptoms. 2.Microscopic evidence of an eosinophilic infiltrate in one or more areas of the GI tract (20 or more eosinophils per high power field). 3.Exclusion of other causes of eosinophilia or involvement of other organs.

Etiology : Etiology and pathogenesis of EG is not clear. 50% of patientshave a history of allergy or atopy. The disorder may be associated with autoimmune connective-tissue diseases, such as scleroderma, dermatomyositis, and polymyositis. It has been suggested that immunologic mechanisms involving interleukins 4 and 5 are responsible for EG, and may result from food antigen exposures, stimulating eosinophil degranulation and release of toxic major basic protein into gastrointestinal tissues. Mast cell may be involved in eosinophil chemotaxis and activation.

Site : The disease can affect any part of the gastrointestinal tract from esophagus to colon.It commonly affects gastricantrum and the proximal part of small bowel. Biliary tree and pancreas may also be involved.

Classification: In 1970 Klein et al. divided this disease into three types depending on the layer of the intestinal wall that is mostextensively infiltrated by eosinophils-1. mucosa-predominantdisease 2.muscularis propria-predominant disease 3.serosa-predominantdisease.

In 1982 Kraviset al. modified this classification and correlated the symptoms with the pathologicalsubtype.

1.Mucosal predominant EG:(Common type) Clinical Presentation: Diarrhea, bleeding, malabsorption. Gross: Mucosa - granular and friable, or nodular. Microscopic features: Mucosal eosinophils, blunting of villi in the small intestine, crypt abscesses, erosions and ulceration.

2. Mural EG: Clinical presentation: Abdominal pain, obstruction, nausea, and vomiting. Gross: Bowel lumen narrow, bowel wall thickened and edematous.Microscopic features: Eosinophilic infiltrate involves the submucosa and muscular wall. The mucosa may appear normal in both mural and serosal types.

3.Serosal EG: Least common.Clinical presentation: Abdominal pain, eosinophilic ascites and obstruction. Gross: Fibrinous exudate or thick plaques may be present on the peritoneal surface of the intestine. Microscopic features: Serosal connective tissue is massively infiltratedby eosinophils.

Summary of Histopathological features:

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Focal and patchy infiltrate ; Increased numbers of eosinophils (often > 50 eosinophils per high-power field) in the lamina propria ; Both intact and degranulating eosinophils may be present within the lamina propria ; Localized eosinophilic infiltrates may cause crypt hyperplasia, epithelial cell necrosis, and villous atrophy ; Eosinophilic infiltration of epithelium, eosinophilic micro-abscesses, crypt abscesses, erosions, and frank ulceration may be present ; Diffuse eosinophilic infiltrates may cause complete loss of villi, submucosal edema, infiltration of the GI wall, and fibrosis may be apparent ; There may be mast cell infiltrates and hyperplastic mesenteric lymph nodes infiltrated with eosinophils.

Note: Establishing a diagnosis of eosinophilic gastroenteritisby endoscopic biopsy may be a problem. In about 10 percentof the cases the mucosal biopsies are nondiagnostic becauseof either sampling error or sparing of the mucosa. In such cases the diagnosis may be established by full-thicknessbiopsy (at least 6 biopsy specimens from normal and abnormal areas of the bowel) or surgical resection.

Differential diagnosis:

Several heterogeneous conditions may cause tissue eosinophilia in the intestines.

1.Chronic Inflammatory Bowel Disease: Eosinophils may be a prominent component of the inflammatory infiltrate in both ulcerative colitis and Crohn's disease. EG is characterised by a florid tissue and peripheral blood eosinophilia with some histopathological similarities to chronic inflamatory bowel disease. Unlike Crohn's disease granulomas, pseudopyloric metaplasia, architectural distortion, and fibrosis are usually not features of EG. Inflammatory infiltrate of Crohn's disease is usually mixed and not exclusively eosinophils. The crypt architectural distortion of Ulcerative colitis is not present in EG.

2.Parasitic infections :Nematode infestations, including those due tohookworm, ascaris, strongyloides, toxocara, trichuris, and intestinalcapillaria, should be considered in patients from areas wherethese parasites are endemic. Parasitic infection can be excluded both on tissue sections and stool examination for ova and parasites. Parasitic infectionalmost always produces a peripheral eosinophilia and an elevatederythrocyte sedimentation rate. In eosinophilic gastroenteritisa moderately increased erythrocyte sedimentation rate is presentin only about 25 percent of the patients.

3.Celiac disease: In celiac disease there may be some increase in eosinophils. In EG there is blunting of villous architecture, but there is no evidence of intra-epithelial lymphocytosis & crypt hyperplasia.

4.Drugs: History of drugs intake should be considered (Eg.acetylsalicylic acid , sulfonamides, penicillin, cephalosporin, carbamazepine).

5.Idiopathic hypereosinophilic syndrome: There is involvement of other organs (heart and lung) other than gut.

6.Other disorders that may be accompaniedby eosinophilia include vasculitis (Churg-Strauss syndrome, polyarteritis nodosa), lymphoma and carcinoma. Long-term outlook for patientswith eosinophilic gastroenteritis is favorable. Most patientsrespond dramatically to a short course of corticosteroid therapy,which usually produces clinical remission. Surgical intervention may be requiredin patients with obstructive complications or refractory disease.