Iatrogenic effects on the GI tract are an extremely interesting but under-recognized entity that often masquerade as celiac sprue and/or autoimmune enteropathies. One of the recently described entities is the olmesartan-associated enteropathy caused by anti-hypertensives class of Angiotensin receptor (ARB) blockade drugs. Olmesartan enteropathy patients often presents with diarrhea, weight loss, nausea and vomiting.

Characteristic histologic findings are abundant intraepithelial lymphocytes in the duodenum, stomach, and colon. In addition, there is mild to moderate active (i.e. neutrophilic) inflammation. Associated findings in the small intestine are villous atrophy/distorted villi, increased sub-epithelial collagen and extensive crypt dropout. The large intestine shows crypt architectural distortion, crypt abscess, consistent with chronic active colitis and suggestive of inflammatory bowel disease.

The differential diagnosis of patients with unexplained chronic diarrhea who are taking olmesartan-containing medications includes olmesartan-associated enteropathy, celiac disease, tropical srpue, Crohns, autoimmune enteropathy and Mycophenolate toxicity. Clinicopathologic correlation and effective communication with gastroenterologists are the cornerstone for recognizing olmesartan-associated enteropathy and a small intervention of stopping ARBs can have a profound impact on the patients' health with resolution of symptoms and histologic alterations.