Olmesartan-induced enteropathy causing chronic diarrhea in an elderly female

Olmesartan-induced enteropathy (OIE) is an uncommon but increasingly recognised cause of chronic diarrhea that closely resembles celiac disease in both clinical presentation and histopathology. Because symptoms often develop months to years after drug initiation, diagnosis may be delayed unless clinicians maintain a high index of suspicion. A 55-year-old woman presented with two months of chronic diarrhea, abdominal cramps, and 8 kg weight loss. She was on Olmesartan for hypertension. Examination showed mild pallor and edema, with anemia and hypoalbuminemia on laboratory testing. Endoscopy was normal, but duodenal biopsy revealed villous atrophy with intraepithelial lymphocytosis. Celiac serology and HLA-DQ2/DQ8 were negative. Suspecting Olmesartan-induced enteropathy, the drug was discontinued, leading to complete symptom resolution within two weeks. OIE is a key differential diagnosis in patients with chronic diarrhea and celiac-like histology but negative celiac serology and HLA typing. Histologic findings may overlap significantly with celiac disease, making a detailed medication review essential. Drug withdrawal typically results in rapid clinical improvement, serving both diagnostic and therapeutic purposes. This case underscores the importance of considering Olmesartan-induced enteropathy in the evaluation of chronic diarrhea, particularly when endoscopy is normal and celiac investigations are negative. Early recognition can prevent misdiagnosis, unnecessary dietary restrictions, and unwarranted invasive testing.