A case of ascending aortic mural thrombosis complicating ulcerative colitis

A 60-year-old man presented with several weeks of watery diarrhea and hematochezia and was referred for emergency admission after lower gastrointestinal endoscopy at a local clinic suggested ulcerative colitis. High-dose corticosteroid therapy was initiated, yielding symptomatic improvement; however, on hospital day 13, contrast-enhanced computed tomography of the chest and abdomen-performed to evaluate extraintestinal manifestations-revealed ascending aortic mural thrombus. Although the patient exhibited no embolic events, the size and morphology of the thrombus conferred a high risk of catastrophic embolization, prompting urgent surgical intervention. To facilitate rapid tapering of prednisolone and optimize perioperative immunomodulation, a humanized monoclonal antibody targeting the p40 subunit of interleukin-12/23 was administered, allowing reduction of corticosteroids to maintenance levels. The patient subsequently underwent ascending aortic replacement with a prosthetic graft. Histopathological examination demonstrated only mild atherosclerotic change at the thrombus attachment site and discontinuity of the internal elastic lamina, confirming a diagnosis of non-aneurysmal aortic mural thrombus. Given the extreme rarity of ascending aortic thrombosis in the context of ulcerative colitis, this case is presented with a brief review of the literature.