Eosinophilic esophagitis overview

# Overview
Eosinophilic esophagitis (EoE) is an immunoallergic disorder resulting from the interaction between genetics and environmental triggers such as repeated exposure to food and aeroallergens. The documented cytokine expression profile in the esophageal tissue of EoE patients is that of a TH2 inflammatory response. IL-5 and IL-13 are produced by the type-2 helper T cells (Th2) in response to the antigenic proteins from the food or inhalation. Cytokines produced by TH-1 cells are tumor necrosis factor (TNF)-, Interferon (IFN)-. CD34+ myeloid precursor cells in the bone marrow produce eosinophils and then the eosinophils develop granulation and migrate to vascular spaces. Eosinophils cause inflammation in the EoE patients by the following mechanisms angiogenic molecules from the eosinophils recruits the inflammatory cells and the increase the vascularity. Fibrogenic mediators such as TGF-1 and matrix metalloproteinase 9 (MMP)-9 causes the airway remodeling. The esophageal mucosa in patients with a longstanding EoE is characterized by a loss of elasticity. On histologic examination of the subepithelial compartments of the esophagus show an increase in the fibrous tissue. There is no established system for the classification of Eosinophilic esophagitis (EoE). The causes of EoE include food and pollens. Eosinophilic esophagitis must be differentiated from other diseases that cause dysphagia such as reflux esophagitis, esophageal carcinoma, systemic sclerosis, esophageal spasm, pseudoachalasia, stroke, esophageal candidiasis and chagas disease. The incidence Eosinophilic esophagitis (EoE) is approximately 10 per 100,000 individuals worldwide. The prevalence of EoE is approximately 50-100 per 100,000 individuals worldwide. The risk factors of EoE are as follows bimodal age distribution, male gender, cold and dry climate. The history and symptoms of eosinophilic esophagitis (EoE), dysphagia, regurgitation, cough, chest pain, food impaction, upper abdominal pain, vomiting.The complications of the EoE includes Scarring of esophagus-leading to dysphagia, Esophageal stenosis, Tears or perforation during the endoscopy or retching leading to boerhaave syndrome.As relatively newly recognized disease, there is very limited data on the causes, natural history, prognosis, diagnosis and management of these patients. The long-term prognosis of the EoE is unclear but patients diagnosed with EoE have an unaffected lifespan.  Patients who are untreated or have discontinued the treatment have progression of their symptoms. The EoE patients with a narrow esophageal lumen are resistant to the corticosteroid treatment and require many esophageal endoscopic procedures. There are no specific diagnostic markers to diagnose the EoE patients, however, an increased peripheral eosinophil count is also seen in majority patients. The barium swallow of the esophagus shows multiple rings associated with eosinophilic esophagitis, There are no MRI nor CT scan findings associated with EoE. however, an MRI or a CT scan may be helpful in the diagnosis of complications of EoE such as tears, perforation strictures etc. The optimal treatment of eosinophilic esophagitis remains uncertain.  An eight-week course of therapy with topical corticosteroids (fluticasone or budesonide) may be used as the first-line pharmacologic therapy.  Allergen elimination usually leads to improvement in dysphagia and reduction of eosinophil infiltration.  Esophageal dilation of is generally reserved for refractory cases with esophageal stricture.

# Historical Perspective
In 1981, Picus and Frank reported a case of a 16-year-old boy with progressive dysphagia for 1.5 years, endoscopic findings were suggestive of multiple 1-mm nodular filling defects in the esophagus in an area of stricture with dilatation above. The radiology showed a luminal narrowing, wall rigidity, and high circulating eosinophil count assumed to be a variant of eosinophilic gastroenteritis.

# Classification
There is no established system for the classification of Eosinophilic esophagitis (EoE).

# Pathophysiology
Eosinophilic esophagitis is an immunoallergic disorder resulting from the interaction between genetics and environmental triggers such as repeated exposure to food and aeroallergens. Patients presenting with EoE have a history of elevated serum IgE levels, response to interventions such as diet restriction, history of food hypersensitivity. Eosinophils originate from CD34+ myeloid precursor cells in the bone marrow, mature to a granulated state and migrate to vascular spaces. The eosinophils are absent in an otherwise normal esophagus, the presence of the eosinophils in the esophagus suggests GERD or EoE. They tend to be present in all layers of the esophagus in EoE, but predominate in the lamina propria and submucosal regions. The documented cytokine expression profile in the esophageal tissue of EoE patients is that of a TH2 inflammatory response. IL-5 and IL-13 are produced by the type-2 helper T cells (Th2) in response to the antigenic proteins from the food or inhalation. IL-13 further stimulates the epithelial cells of the esophagus to produce large proteins to induce a gene called eotaxin-3, which in turn recruits eosinophils from the peripheral blood into the tissue. IL-5 prolongs the survival of the eosinophils. The activated TH2 response leads to the recruitment and activation of Mast cells degranulate and cause tissue damage and repair. Cytokines produced by TH-1 cells are tumor necrosis factor (TNF)-, Interferon (IFN)-, TNF- is expressed by the epithelial cells of the esophagus whereas the INF- is upregulated by the peripheral T cells. Delayed or type- IV hypersensitivity is the mechanism is involved in the EoE rather than the non-IgE. It is postulated that the EoE-defining endoscopic and histologic manifestations are a culmination of the disease process which, may have debilitating long-term effects including strictures and food impactions in untreated or poorly managed cases of EoE. CD34+ myeloid precursor cells in the bone marrow produce eosinophils and then the eosinophils develop granulation and migrate to vascular spaces. Eosinophils although present in all the layers of the esophagus in patients with EoE, they are predominant in the lamina propria and submucosa of the esophagus. The preformed granule proteins of the eosinophils are ECP- Eosinophil Cationic Protein, MBP- Major Basic Protein, EPO- Eosinophil Peroxidase, EDN- Eosinophil Derived Neurotoxin. Upon the stimulation and the degranulation, the eosinophils release the granule proteins into the tissues. Eosinophils synthesize and release cytokines such as IL-5, IL-13, Transforming growth factor (TGF)- and -, Chemokines (eotaxins and RANTES), Lipid mediators such as platelet activating factor (PAF) and leukotriene C4. IL-5, IL-13, and granulocyte-macrophage colony stimulating factor (GM-CSF) can cause the maturation and migration of the eosinophils. Eosinophils cause inflammation in the EoE patients by the following mechanisms Angiogenic molecules from the eosinophils recruits the inflammatory cells and the increase the vascularity. Fibrogenic mediators such as TGF-1 and matrix metalloproteinase 9 (MMP)-9 causes the airway remodeling. MBP and MMP-9 disrupt the integrity of the epithelial cells of the esophageal through their involvement in smooth muscles, fibroblasts, and cell-adhesion molecules. The above-mentioned processes lead to tissue remodeling eventually causing an overall esophageal dysfunction.

# Causes
The causes of EoE are the food and pollen react with the lining of the esophagus, these allergens cause the multiplication of eosinophils in the layers of the esophagus and produce a protein that causes inflammation. The inflammation further cause scarring, excessive fibrous tissue deposition over the lining of the esophagus eventually leading to dysphagia. The dysphagia can sometimes worsen to cause food impaction and additional symptoms such as chest pain.

# Differentiating Eosinophilic esophagitis overview from Other Diseases
Eosinophilic esophagitis must be differentiated from other diseases that cause dysphagia such as reflux esophagitis, esophageal carcinoma, systemic sclerosis, esophageal spasm, pseudoachalasia, stroke, esophageal candidiasis and chagas disease.

# Epidemiology and Demographics
The incidence Eosinophilic esophagitis (EoE) is approximately 10 per 100,000 individuals worldwide. The prevalence of EoE is approximately 50-100 per 100,000 individuals worldwide. Patients of all age groups may develop EoE. It usually affects individuals of the white race. Males are more commonly affected by EoE than females. EoE is a rare disease that tends to affect people with a history of European ancestry.

# Risk Factors
The risk factors of EoE are as follows bimodal age distribution common in both children and adults, male gender, cold and dry climate, EoE is common in people with a history of European ancestry, summer and fall, positive family history of EoE, history of allergies such as asthma, industrial exposures, environmental allergies, chronic respiratory disease, food allergies and atopic dermatitis.

# Screening
There is insufficient evidence to recommend routine screening for Eosinophilic esophagitis (EoE).

# Natural History, Complications, and Prognosis

## Natural History
The natural course of primary EoE is, in patients with EoE, symptoms persist over years raising suspicion that a chronic inflammatory process is an underlying event responsible for it. The inflammatory activity is proportional to the density of the eosinophilic infiltration in the esophageal tissue. Similar to asthma, EoE has chronic persistent eosinophilic inflammation and can eventually lead to irreversible structural changes of the esophagus which is called re-modeling of the esophagus. The esophageal mucosa in patients with a longstanding EoE is characterized by a loss of elasticity. On histologic examination of the subepithelial compartments of the esophagus show an increase in the fibrous tissue. In patients with EoE, the chronic eosinophilic inflammation leads to an increased deposition of the fibrous connective tissue which in turn causes the remodeling of the esophagus hindering the esophageal transport.

## Complications
The complications of the EoE are as follows: Scarring of esophagus-leading to dysphagia, Esophageal stenosis, Tears or perforation during the endoscopy or retching leading to boerhaave syndrome.

## Prognosis
The long-term prognosis of the EoE is unclear but patients diagnosed with EoE have an unaffected lifespan.

# Diagnosis

## Diagnostic Criteria

## History and Symptoms
The history and symptoms of eosinophilic esophagitis (EoE), dysphagia, regurgitation, cough, chest pain, food impaction, upper abdominal pain, vomiting. Clinical features in children are follows abdominal pain, nausea, emesis, failure to thrive. Clinical features in the adolescents and adults are as follows dysphagia, heartburn, food impaction, strictures.

## Physical Examination
The physical examination of the patients with EoE is usually normal.

## Laboratory Findings
There are no specific diagnostic markers to diagnose the EoE patients. Although not specific, elevated serum IgE levels are identified in majority patients. An increased peripheral eosinophil count is also seen in majority patients. There are 3 main ways in which food allergies can be detected in EE are Skin prick testing, Blood allergy testing, Atopy patch testing.

## Imaging Findings
The barium swallow of the esophagus shows multiple rings associated with eosinophilic esophagitis, There are no MRI or CT scan findings associated with EoE. however, an MRI or a CT scan may be helpful in the diagnosis of complications of EoE such as tears, perforation strictures etc

## Other Diagnostic Studies

# Treatment

## Medical Therapy
The optimal treatment of eosinophilic esophagitis remains uncertain.  An eight-week course of therapy with topical corticosteroids (fluticasone or budesonide) may be used as the first-line pharmacologic therapy.  Allergen elimination usually leads to improvement in dysphagia and reduction of eosinophil infiltration.  Esophageal dilation of is generally reserved for refractory cases with esophageal stricture.

## Surgery
Surgical intervention is not recommended for the management of Eosinophilic esophagitis.

## Prevention
There are no established measures for the primary prevention of Eosinophilic esophagitis (EoE).