Myointimal hyperplasia of the mesenteric veins mimicking inflammatory bowel disease in a 13-year-old patient.

Idiopathic myointimal hyperplasia of the mesenteric veins (IMHMV) is a rare entity reported in adults, frequently mimicking inflammatory bowel disease (IBD). We report the first case of intestinal ischemia secondary to IMHMV presenting as IBD in a pediatric patient with Down syndrome. Chronic intestinal ischemia is rare in children, and this case emphasizes the need to consider this in the differential, when histopathology is suggestive. Clinical findings and colonoscopy in these patients may mimic IBD. The mucosal biopsies do not show classic features of IBD. Instead, there can be variable extent of mucosal changes such as dilated small capillaries in the lamina propria, edema, and early fibrosis. These changes may in fact represent early chronic ischemia. These findings should alert for vascular imaging and a full-thickness biopsy to assess submucosal and subserosal larger vessels since medium- and large-caliber veins in the colonic wall and mesentery are affected in IMHMV.