The idiopathic myointimal hyperplasia of mesenteric veins is a rare pathology, affecting recto-sigmoid and mimicking clinically an inflammatory chronic disease of the bowel. Only about fifteen cases have been reported in the literature. This lesion is characterized by a myointimal thickening of the mesenteric veins, without inflammatory infiltrate of the vascular wall, differentiating it from vasculitis. We present here the case of a 48-year-old man, in whom the diagnosis of ulcerative colitis then digestive vasculitis had first been raised.