Chronic diarrhea is frequented in the Gastroenterology clinic. Sometimes, the diagnosis may be challenging as there are multiple entities with unremitting diarrhea as a symptom. 

A recent article described a case of a patient affected with intractable diarrhea. After undergoing many laboratory, endoscopy and radiological tests, she was diagnosed with autoimmune enteropathy (AE) and acquired clinical remission with corticosteroids and azathioprine. 

AE is a rare cause of intractable diarrhea with a complex and poorly understood pathophysiology. it causes dysregulation in both humoral and cell-mediated immunity. The overexpression of MHC-II molecules causes the proliferation of CD4+ and CD8+T lymphocytes that exert their effect, either via direct cytotoxicity by secreted lymphokines or via indirect antibody-dependent cytotoxicity. patients affected with AE may also have some other autoimmune diseases such as diabetes or hypothyroidism. 

In AE, Patients suffer from persistent diarrhea with nil dietary response and specific intestinal histology. Several other entities like celiac disease, drug enteropathy (e.g., olmesartan), inflammatory bowel disease, collagenous colitis and intestinal lymphoma or common variable immunodeficiency must be ruled out. Antibodies against intestinal epithelium can aid in diagnosing but their absence does not rule out the diagnosis of AE. 

Intestinal mucosa can be normal at endoscopy. However, features like duodenal scalloping, ulcerations and edema, mosaic pattern and villous atrophy are frequently reported along the small intestine. Furthermore, mucosa changes can involve whole of the digestive system. Complete or partial villous atrophy, intraepithelial lymphocytes, crypt hyperplasia and plasmatic cell infiltration in lamina propria are described to be the primary hallmarks of AE. However, these histological features can be absent in the early phases of the disease.

Treatment of AE mainly utilizes corticosteroids (budesonide/ prednisone), with or without azathioprine/mercaptopurine. 

Some patients do not respond to the initial treatment, which leads to a poor prognosis and the development of severe malnutrition. Thus total parenteral nutrition must be administered for long periods. 

Source: Rev Esp Enferm Dig. 2021 May;113(5):348-351. doi: 10.17235/reed.2020.7218/2020. PMID: 33256418.