S4867 Idiopathic Myointimal Hyperplasia of the Mesenteric Veins (IMHMV) Mimicking Inflammatory Bowel Disease: A Tertiary Referral Experience

Introduction: Idiopathic myointimal hyperplasia of the mesenteric veins (IMHMV) is a rare entity causing gastrointestinal mucosal inflammation and mimicking inflammatory bowel disease (IBD). We characterize 3 patients treated at a tertiary referral center with IMHMV. Case Description/Methods: Patient 1: A 67-year-old man presented with subacute lower abdominal pain, weight loss, and diarrhea. Contrasted computed tomography (CT) showed diffuse wall thickening from the transverse colon to the rectum. Colonoscopy revealed diffuse moderate inflammation[in the same regions. Biopsies showed nonspecific regenerative changes potentially consistent with a resolving ischemic or infectious process. Earlier biopsies had an ischemic colitis pattern. He received antibiotics and prednisone without benefit and underwent extended left colectomy. Surgical pathology demonstrated thick-walled submucosal veins, consistent with IMHMV. Patient 2: A 35-year-old man presented with 5 weeks of diarrhea, rectal bleeding, weight loss, nausea, vomiting and abdominal pain. CT demonstrated contiguous bowel wall thickening from rectum to the splenic flexure. Colonoscopy revealed severely ulcerated mucosa in the sigmoid and descending colon with rectal sparing. Sigmoid biopsies showed ulcerated mucosal tissue without features of chronicity. Antibiotics and steroids were without sustained benefit. He underwent extended left colectomy with pathology consistent with IMHMV. Patient 3: A 71-year-old man was referred for recurrent small bowel obstructions. CT showed small bowel tethering by a mesenteric mass. This mass was most suggestive of a neuroendocrine tumor or sclerosing mesenteritis. He underwent a 60 cm jejunal resection and pathology demonstrated diffuse xanthogranulomatous histiocytic infiltrate and concurrent IMHMV without neoplastic process. Discussion: Over half of patients with IMHMV are misdiagnosed with IBD, with associated complications related to medication use. Here we present 2 relatively classic cases of IMHMV in that the patients were men with diarrhea, weight loss and abdominal pain on presentation, contiguous left-sided colonic involvement but pathology inconsistent with IBD. Also highlighted is a third case of a patient with rare small bowel IMHMV and concurrent xanthogranulomatous inflammation, a rare disease process known to simulate neoplastic processes that infrequently occurs in the gastro-intestinal tract. To our knowledge, this is the first reported association of IMHMV and xanthogranulomatous inflammation.