S6239 Unmasking the Silent Culprit: Olmesartan-Induced Gastroenteropathy

Introduction: Olmesartan has been associated with the development of a unique seronegative celiac-like enteropathy called olmesartan-induced enteropathy (OIE). This rare condition can manifest with chronic diarrhea and abdominal pain which may be misdiagnosed as irritable bowel syndrome. Diagnosing OIE is challenging, necessitating a process of exclusion as histopathological examination of biopsied tissue is similar to celiac disease. We present a case of a patient on long-term olmesartan who developed chronic diarrhea and significant weight loss requiring multiple hospitalizations. Case Description/Methods: A 47-year-old woman presented to the clinic with chronic diarrhea for 4 months with recent worsening nausea, vomiting, abdominal pain, decreased oral intake, and weight loss. Her home medications included olmesartan 40 mg, which she had been taking for more than 10 years for hypertension. She was hospitalized a week prior and underwent negative stool studies for Clostridioides difficile, computed tomography of the abdomen and pelvis was unremarkable, and sigmoidoscopy with random biopsies was normal. Fecal calprotectin was 608. She was empirically treated with metronidazole without improvement and subsequently discharged off olmesartan with improvement of diarrhea. After discharge, she became hypertensive and olmesartan was restarted. She was seen in gastroenterology clinic 1 month later with severe diarrhea, dehydration, 25 lb weight loss, and was admitted to the hospital with hypotension. Olmesartan was stopped; magnetic resonance enterography was unrevealing; infectious stool studies were negative and celiac serologies were negative. Esophagogastroduodenoscopy and colonoscopy revealed diffuse gastric erythema and normal appearing small bowel. Colonoscopy was unremarkable. Biopsies revealed total villous blunting in the duodenum and ileum and diffuse active chronic gastritis. Given the severity of the disease, she was prescribed a prednisone taper and olmesartan was discontinued due to strong suspicion of OIE. At a follow-up clinic visit, the patient reported significant improvement in her symptoms. Discussion: Our case report presents a patient with a history of chronic olmesartan use who developed persistent diarrhea after more than 10 years of treatment. This case underscores the importance of recognizing medication-induced enteropathies in patients exhibiting celiac-like features, allowing for early detection and optimal management, even in cases with extended exposure to susceptible medications.