Eosinophilic gastroenteritis (EGE) is an uncommon inflammatory gastrointestinal (GI) disease affecting both children and adults. This condition is characterized by the following:
Eosinophilic infiltration in one or more areas of the GI tract, mainly the stomach and duodenum and, in some cases, the esophagus and colon, defined as 20 or more eosinophils per high-power field (HPF)
The presence of abnormal GI symptoms, most often abdominal pain, nausea, vomiting, diarrhea, and weight loss
The absence of an identified cause of eosinophilia
The exclusion of eosinophilic involvement in organs other than the GI tract
A history of atopy or food allergies is often present.
Clinical symptoms are determined by the anatomic locations of eosinophilic infiltrates and the depth of GI involvement: mucosal, muscularis, or serosal. 
Kaijser was probably the first to report a patient with eosinophilic gastroenteritis in 1937; since then, the number of case reports has increased. Treatments are often unsatisfactory, and long-term outcomes are uncertain.
The underlying molecular mechanism predisposing to the clinical manifestation of eosinophilic gastroenteritis is unknown. Eosinophilic gastritis, enteritis, and gastroenteritis are diseases characterized by the selective infiltration of eosinophils in the stomach, small intestine, or both.  The disorders are classified into primary and secondary subtypes. The primary subtypes, which have also been called idiopathic or allergic gastroenteritis, include the atopic, nonatopic, and familial subtypes.
In patients, manifestations of their diseases are based on histologic involvement: mucosal, muscularis, or serosal forms.  Any layer of the GI tract can be involved. The secondary subtypes may be divided into 2 groups: systemic eosinophilic disorders (ie, hypereosinophilic disorders) and noneosinophilic disorders (eg, celiac disease, inflammatory bowel disease, vasculitis).
Although these diseases are idiopathic, recent investigations support the role of eosinophils, T helper 2 (Th2) cytokines (interleukin [IL]-3, IL-4, IL-5, and IL-13), and eotaxin as the critical factors in the pathogenesis of eosinophilic gastroenteritis. Eosinophils function as antigen presenting cells as they express major histocompatibility complex (MHC) class II molecules.
Eosinophils can mediate proinflammatory effects, including the up-regulation of adhesion systems, modulation of cell trafficking, and cellular activation states by releasing cytokines (IL-2, IL-4, IL-5, IL-10, IL-12, IL-13, IL-16, IL-18, and transforming growth factor [TGF]-alpha/beta), chemokines (RANTES and eotaxin), and lipid mediators (platelet activating factor [PAF] and leukotriene C4).
Finally, eosinophils can serve as major effector cells, inducing tissue damage and dysfunction by releasing toxic granule proteins (major basic protein [MBP], eosinophilic cationic protein [ECP], eosinophil peroxidase [EPO], and eosinophil-derived neurotoxin [EDN]) and lipid mediators, which are cytotoxic.
Atopy is present in a subset of patients, as these patients demonstrate increased total immunoglobulin E (IgE) on food-specific IgE radioallergosorbent assay test (RAST) or skin tests. Furthermore, lamina propria T cells from the duodenum of these patients proliferated in response to milk proteins and secreted Th2 cytokines (IL-13).
However, other studies suggest a non–IgE-mediated mechanism. Upregulation of thymic stromal lymphopoietin (TSLP) has been observed in these patients.
The cause or mechanism of eosinophilic infiltration is not known.
Patients with eosinophilic gastroenteritis have elevated IgE and eosinophilia of tissue and blood. An imbalance in the T-cell paradigm causing an increase in the production of IL-13, IL-4, and IL-5 and cytokines has been postulated as the cause of IgE synthesis and eosinophilia.
In one study, immunohistochemistry detected IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-5 in the granule matrix of eosinophils, the release of which is thought to be involved in the perpetuation of intestinal eosinophil infiltration and inflammation.
United States data
The disease is rare, and the incidence is difficult to estimate. However, since the description of eosinophilic gastroenteritis by Kaijser in 1937, without an accurate database registry, the incidence is estimated to be 1 case per 100,000 and a prevalence of 28 per 100,000 in the United States.
Although cases have been reported worldwide, the exact incidence of eosinophilic gastroenteritis is unclear. A confounding factor is lack of diagnostic precision.
A systematic review that evaluated the racial differences in eosinophilic gastrointestinal disorders between white and Asian populations found that eosinophilic gastroenteritis more commonly affects Asian patients (72%), whereas eosinophilic esophagitis is more common in white patients (94%).  Asian patients with eosinophilic esophagitis exhibited significantly fewer symptoms of heartburn and dysphagia but more vomiting and abdominal pain compared to white patients. In addition, Asian patients with eosinophilic gastroenteritis were significantly more likely to have eosinophil infiltration of the colon, but the stomach was less likely to be affected. 
Kim et al reported 31 new cases of eosinophilic gastroenteritis in Seoul, Korea, between January 1970 and July 2003. 
Chen et al reported on 15 patients, including 2 children, with eosinophilic gastroenteritis who were evaluated over an 18-year period at a hospital in China in 2003. 
Venkataraman et al reported 7 new diagnoses of eosinophilic gastroenteritis over a 10-year period in India. 
Race-, sex-, and age-related demographics
Cases of eosinophilic gastroenteritis are reported mostly in white individuals, with some cases occurring in Asians.
A slight male preponderance has been reported.
Patients present clinically in the third to fifth decades of life, but the disease can affect any age group, from infancy through the seventh decade.
The natural history of eosinophilic gastroenteritis (EGE) has not been well documented. Eosinophilic gastroenteritis is a chronic, waxing and waning condition. Mild and sporadic symptoms can be managed with reassurance and observation, whereas disabling gastrointestinal (GI) symptom flare-ups can often be controlled with oral corticosteroids. When the disease manifests in infancy and specific food sensitization can be identified, the likelihood of disease remission by late childhood is high.
There are very few published studies on the natural progression of EGE. In a retrospective study of 43 patients over a mean duration of 13 years, De Chambrun et al noted three patterns: 42% of patients suffered a single outbreak of EGE shorter than 3 months, 37% patients experienced intermittent flares, and 21% had persistent active symptoms. 
Morbidity includes malnutrition and intestinal obstruction and perforation. Fatal outcomes are rare, GI obstruction is the most common complication, and the risk of cancer is not increased.
Some patients with EGE may present with bloody diarrhea, mimicking inflammatory bowel disease. Another complication includes intestinal perforation, which usually requires surgical repair. Extraintestestinal presentations can also occur, such as eosinophilic hepatitis, cholecystopancreatitis with bile duct dilatation obstruction and jaundice.
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