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.