Eosinophil gastrointestinal diseases (EGID) is an umbrella term that encompasses a plethora of primary conditions associated with inappropriate activity of eosinophils. Eosinophils are white blood cells that share a number of functions with mast cells. They are important to immune response to infections, especially parasites, as well as allergy. Eosinophils typically account for 6% or less of the total white blood cell count. They are found in a number of places in the body, but are not usually found in the lung, skin or esophagus without some underlying pathology. Like mast cells, they have granules filled with chemicals and can degranulate in response to stimulus. They release some chemicals in common with mast cells and some not.
Eosinophils are increased in a number of GI conditions, including allergy associated colitis in adults, allergic proctocolitis in infants, eosinophilic gastroenteritis and eosinophilic esophagitis. They are also elevated in inflammatory bowel disease, reflux esophagitis, celiac disease and other types of colitis. Increased eosinophils can be induced by several other conditions or disease states, including infection, use of certain medications, collagenous and lymphocytic colitis, connective tissue disease, neoplasia, graft vs host disease and autoimmune colitis. It can also be associated with allergy or idiopathic. Despite a fair amount of research, many papers use varying criteria for determination of disease and excess eosinophil count. This ambiguity has contributed to much confusion and will be discussed in detail in upcoming posts. Still, pathologically, eosinophils are rarely found in number in any tissue sample and if present indicate inflammation or disease.
A number of conditions can cause secondary increase of eosinophils in the GI tract. EGIDs are primary conditions and are listed below.
Eosinophilic gastroenteritis most often affects adults, with females being slightly more likely to develop it. Infants rarely have this condition, but some have been identified. Virtually the entire GI tract can be affected, but most often the stomach and small intestine. The eosinophils can be diffuse and localized to only one organ or portion of the organ. They can cause lesions mistaken for tumors. This condition is characterized by edema, “numerous” eosinophils in almost any layer, and ulcerations that can look like tumors. Eosinophilic gastroenteritis is idiopathic, but 50-70% are thought to be due to allergic responses, especially from medications.
Eosinophilic esophagitis usually first presents in people under 30. Males are more commonly affected. It is defined as 15 or more eosinophils/hpf (peak count) with eosinophils mostly found in the mucosa or muscular wall of the esophagus. Microabscesses and basal cell hyperplasia are sometimes found. It is subclassified as being allergic or non-allergic.
Eosinophilic colitis is a more controversial entity marked by nonspecific symptoms, unclear diagnostic criteria, and relapsing-remitting course. It is exceptionally rare. This will be discussed in detail in an upcoming post.
Eosinophilic gastroenteritis has much the same profile as eosinophic gastroenteritis, but the disease process is limited to the small intestine.
Allergic proctocolitis affects the rectum and/or colon of children under 2 years of age. Eosinophils can be found diffusely or focally in these patients. It is defined as more than 6 eosinophils/hpf in the lamina propria layer, and/or “elevated” eosinophils in the intraepithelial or muscular layers (considered 1-2 or “numerous” in various studies.) This is the result of food allergy, especially cow’s milk or soy.
Mueller, Susanna. Classification of eosinophilic gastrointestinal diseases. Best Practice & Research Clinical Gastroenterology 2008, 22 (3): 425-440.
Spergel, Jonathan, et al. Variation in prevalence, diagnostic criteria, and initial management options for eosinophilic gastrointestinal diseases in the United States. JPGN 2011, 52 (3): 300-306.
Alfadda, Abdulrahman. Eosinophilic colitis: epidemiology, clinical features and current management. Ther Adv Gastroenterol 2010, 4(5) 301-309.