Abstract
Lemierre's syndrome (LS) is a rare but potentially fatal condition characterized by septic thrombophlebitis of the internal jugular vein (IJV), most often secondary to oropharyngeal infection. It is typically associated with Fusobacterium necrophorum and may lead to septic emboli, predominantly in the lungs. We report a rare case of a previously healthy 33-year-old man with LS complicated by extensive multivessel thrombosis, including the internal jugular, brachiocephalic, and superior vena cava (SVC) veins, with propagation of thrombus into the right atrium, in addition to septic pulmonary emboli. This constellation of findings is exceedingly rare and underscores the propensity of LS to extend beyond cervical veins into central thoracic and cardiac structures. Despite persistently negative blood cultures, likely due to prior antibiotic exposure, the diagnosis was established through clinical and imaging features. The patient was successfully managed with prolonged intravenous antibiotics, anticoagulation, and a multidisciplinary approach. This case emphasizes the importance of early recognition of atypical and extensive thrombotic complications in LS, as timely intervention can be lifesaving.