Coeliac disease and other intraepithelial lymphocytic disorders of the upper gastrointestinal tract

The finding of increased intraepithelial lymphocytes (IEL) in the upper gastrointestinal tract is common to a wide variety of disorders that involve mucosal injury. Coeliac disease or gluten-sensitive enteropathy is perhaps the first entity in pathologists' differential diagnosis when asked to identify disorders with increased IEL, but it is far from the only condition that can result in such a finding. The numerous causes that can result in this histological feature can be easily organized into three categories. Inflammatory and immune causes include coeliac disease and other autoimmune conditions, as well as relatively rare hematolymphoid neoplasms. Infectious causes include numerous conditions that often have subtle histological findings, such as giardiasis and bacterial overgrowth. Finally, “ingested” causes range from pharmacological agents to morbid obesity, which has also been associated with the isolated finding of increase IEL in the upper gastrointestinal tract. This contribution reviews selected entities from each of these categories, with special attention to coeliac disease.