Pathognomonic Features of Olmesartan-Induced Collagenous Sprue Resulting in Severe Small Bowel Malabsorption

Collagenous sprue (CS) is a rare autoimmune gastrointestinal disorder characterized by specific histologic changes in the small intestine. It often presents with more severe symptoms and a worse prognosis compared to celiac disease, including significant malabsorption, weight loss, and nutrient deficiencies. Despite treatment with a gluten-free diet, symptom improvement is limited, with only a small fraction of patients responding positively. This case report highlights the diagnostic challenges and clinical features of CS in a 74-year-old woman, whose symptoms resolved following cessation of olmesartan. The case emphasizes the importance of recognizing medication-induced forms of the disease and outlines the need for targeted management strategies to improve patient outcomes.