Answer: Eosinophilic esophagitis

Histology: Biopsy of esophageal mucosa shows dramatic clusters of intraepithelial eosinophils.

Discussion: Eosinophilic esophagitis/ gastroenteritis (EG) is an uncommon benign inflammatory condition characterised by eosinophilic infiltration of gastrointestinal (GI) tract. The diagnostic criteria are:

• gastrointestinal symptoms;
• eosinophilic infiltration of the gastrointestinal tract usually with intra-epithelial eosinophils;
• no evidence of parasitic infestation; and
• no infiltration of extraintestinal organs

Most patients (apart from GI involvement) also present with a history of allergy, asthma, drug sensitivities, peripheral eosinophilia and increased IgE levels. Although food intolerance has been postulated as an etiologic factor, most cases lack a specific allergen and the blame is laid on multiple allergens. EG predominantly affects patients in the 3rd to 6th decades. 15-20% of cases are seen in pediatric age group.

Any part of GI tract from the esophagus to the rectum can be involved-stomach and small bowel are commonly involved. EG can show preferential involvement of either mucosa, muscularis or serosa. Symptoms depend on the site and extent of eosinophilic infiltration. Mucosal disease can present as diarrhea, malabsorption, and protein losing enteropathy. Submucosal disease presents as obstruction and abdominal pain, and patients can develop eosinophilic ascites with serosal involvement. Rarely patients can present with an acute abdominal emergency necessitating emergency laparotomy.

Patients with eosinophilic esophagitis (limited to esophagus) present with dysphagia and strictures. The chief d/d is reflux esophagitis. However, unlike in reflux esophagitis, the upper and mid esophagus are commonly affected with distal sparing. Superficial clusters of eosinophils are more common and eosinophilic infiltration is present deep in the esophageal wall and not just limited to mucosa in eosinophilic esophagitis. It is important to make the distinction as patients with EG show dramatic response to steroids.

Hypereosinophilic syndrome is characterized by peripheral eosinophilia and diffuse infiltration to various tissues such as myocardium, lungs, and gastrointestinal tract.

Histologically, the eosinophilic infiltrate in EG can be patchy and multiple, localized or diffuse. Additional features are edema, eosinophils within epithelium and crypts. In 10% of cases, mucosal biopsies can be nondiagnostic due to the patchy nature of the disease or mucosal sparing. Multiple and full thickness biopsy may be necessary to establish the diagnosis.

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