Soru

A 64-year-old woman comes to the clinic due to a 4-month history of frequent, watery, non-bloody diarrhea. She reports having up to 8 loose bowel movements per day, which occasionally wake her from sleep. She has no fever, abdominal pain, nausea, or unintended weight loss. Her past medical history is notable for osteoarthritis, for which she takes daily ibuprofen, and hypertension managed with lisinopril. Vital signs are within normal limits. Abdominal examination is unremarkable. Laboratory studies, including a complete blood count, comprehensive metabolic panel, and thyroid function tests, are normal. Stool studies are negative for infectious etiologies. A colonoscopy reveals an entirely normal-appearing colonic mucosa throughout. Random biopsies are obtained from the right and left colon. Histopathologic examination of the biopsy specimens shows a preserved crypt architecture, an increased number of intraepithelial lymphocytes, chronic inflammation in the lamina propria, and a notably thickened subepithelial eosinophilic band measuring 15 micrometers (normal is typically less than 5 micrometers). Which of the following is the most likely diagnosis based on these histopathologic findings?