The following are conditions that can cause a secondary increase in eosinophil count in the GI tract. These conditions should be ruled out before giving a diagnosis of EGID, which is inherently primary.
Allergy associated colitis affects adults, with females accounting for 2.5x more patients than males. The age of diagnosis ranges from 20s to 60s. It affects the colon and ileum, with rectum being unaffected. Eosinophils are found in the mucosal, muscular and submucosal layers. Studies have defined it as anywhere from 10-60 eosinophils/hpf, more than one eosinophil/hpf in the intraepithelial layer, or merely having clusters and evidence of degranulation. It is thought to be driven by an allergic response and has been found in association with NSAID allergy.
Hypereosinophilic syndrome (HES) can sometimes affect the colon. People with this condition produce too many circulating eosinophils, as evidenced by persistently high eosinophil count and affect to one or more of the heart, nervous system or bone marrow. Rarely, it can cause elevated eosinophils in the mucosal layer or deep bowel wall of the colon. The mechanism behind this is unclear, but thought to be due to IL-5 stimulating eosinophils inappropriately.
Crohn’s disease can affect the entirety of the GI tract and mostly presents initially in young adults. It can affect continuous or discontinuous portions of tissue. Ulceration, erosion, infiltrates of various inflammatory cells, including eosinophils, lymphoid nodules, granulomas, fibrosis, and vascular and neural lesions are often found on biopsy. It is thought to be due to cooperation of several factors.
Ulcerative colitis affects either diffuse or continuous areas of the left sided colon and rectum. Eosinophils are often found in the mucosa or superficial supermucosa. Edema, erosion, ulceration, granulocytes, and presence of plasma cells are common findings. The etiology is unclear.
Collagenous colitis is mostly found in middle aged and elderly patients, which are predominantly female. It can affect the colon and rectum and is usually discontinuous. Eosinophils are found in the mucosal layer, along with subepithelial collagen deposition, white cells in the intraepithelial layer,and various inflammatory infiltrates. It is thought to sometimes be associated with drug reactions.
Lymphocytic colitis can affect a person of any age. It affects diffuse portions of the colon and eosinophils are found in the mucosal layer. Intraepithelial lymphocytes are often found (surface epithelium >20 IELs per 100 epithelial cells). The etiology is unknown.
Autoimmune colitis occurs in conjunction with other autoimmune conditions. It can affect people of all ages, with activity in the small and large bowels. Eosinophils are found in the mucosal layer of affected tissue, with evidence of degranulation and crypt destruction. Mast cells are often found in the same tissue portions.
Graft versus host disease is a complication of bone marrow transplant and can affect anyone who has been a recipient of one. GvHD can affect the entirety of the body, and therefore can affect the whole length of the GI tract. Eosinophils are often identified in the mucosal layers, along with apoptotic crypt destruction, mixed inflammatory infiltrates and interepithelial lymphocytes.
Peripheral/intestinal T-cell lymphoma overwhelmingly affects adults over 50. It predominantly affects small bowel, but also the stomach and colon. Inflammatory infiltrates with many eosinophils and tumor cells are sometimes found. It is sometimes seen along with gluten-sensitive enteropathy.
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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.