Eosinophilic esophagitis (NORD)

Eosinophilic esophagitis, or EoE, is a chronic food allergy associated digestive disorder in which people have large numbers of eosinophils in the esophagus. Eosinophils are a type of white blood cell that play many roles within the immune system and are involved in allergic reactions.

Signs and symptoms of eosinophilic esophagitis can vary quite a bit, and are frequently the same as those for gastroesophageal reflux disease, also known as GERD.

These symptoms are caused by increased inflammation and swelling within the esophagus, and include trouble swallowing, food getting stuck in the throat, nausea, vomiting, poor growth in childhood, weight loss, stomach pain, poor appetite, and malnutrition.

The increase in eosinophils in the esophagus can be caused by a number of things, particularly hypersensitivity reactions or changes to the expression of certain genes.

The hypersensitivity reactions involved are a form of allergic reaction after exposure to a food or environmental allergen. When certain cells come in contact with the allergen they signal other cells, most commonly eosinophils, to accumulate and get activated in the esophagus.

The first exposure to an allergen may take time to create a response. However, some cells remember that allergen to more quickly react to future exposures.

Therefore, the more a person is exposed to allergens which trigger a hypersensitivity reaction, the more eosinophils will be present.

Additionally, changes to gene expression appear to play a role in increasing the number of eosinophils in a person with EoE.

A primary gene involved in people with EoE is CCL26 which encodes for eotaxin-3. Eotaxin-3 is a protein that triggers increased eosinophil production and the gene is often overexpressed, meaning it is used to make more proteins than usual in people with eosinophilic esophagitis.

When eotaxin-3 makes more proteins, those proteins trigger more eosinophils to be recruited to the esophagus, consequently resulting in the increased number of eosinophils present in people with EoE.

Some other genes that are associated with EoE, such as CAPN14, contribute to the loss of esophageal barrier function allowing increased ability for allergens and inflammatory cells, like eosinophils, to enter the esophagus, leading to the development of eosinophilic esophagitis.