A Rare Case of Takayasu Arteritis and Aortic Aneurysm in a Male Patient.

Takayasu arteritis (TA) is a rare large-vessel vasculitis typically affecting young women. Fever of unknown origin (FUO) can be an early manifestation, especially in atypical demographic groups, delaying diagnosis. A 49-year-old male presented with a month-long history of daily intermittent fevers, night sweats, weight loss, anorexia, and dry cough. Laboratory studies showed anemia, elevated inflammatory markers, and hyperferritinemia. Extensive infectious and autoimmune and workup was negative. During oncologic screening, colonoscopy identified a rectal intramucosal adenocarcinoma, which was completely resected. An 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) revealed increased uptake in the thoracic aorta, brachiocephalic trunk, and bilateral carotid and subclavian arteries. Transesophageal echocardiography confirmed a 55-mm ascending aortic aneurysm. The patient later developed pericarditis, upper limb claudication, and right internal carotid artery occlusion, fulfilling the diagnostic criteria for TA. He was treated with corticosteroids and methotrexate, followed by ascending aorta replacement. Follow-up PET/CT showed resolution of inflammation, with sustained remission. This case illustrates the importance of considering TA in FUO. An 18F-FDG PET/CT can be pivotal in diagnosis, enabling early treatment and preventing vascular complications.