In a 70-year-old female the fatigue syndrome lasting for several months was followed by a significant enterorrhagia. A left-sided hemicolectomy was performed for previously diagnosed severe diverticular disease of this part of the colon. Histology revealed mucosal edema and irregular arrangement of submucosal capillaries and venules. During the next 5 months the patient experienced two further attacks of enterorrhagia. Total colonoscopy, capsule and double-balloon enteroscopy did not reveal any source of bleeding. On repeated angiography colonic angiodysplasias were described. The anemia and increased total proteinemia indicated hematologic consultation which resulted in the diagnosis of Waldenström macroglobulinemia. This is the first case of the disease presenting exclusively with colonic bleeding. Angiodysplasias are considered a facilitating factor of the symptom.

        Key words: Waldenström macroglobulinemia, enterorrhagia, colonic angiodysplasias