Background: Typical Lemierre's syndrome is usually secondary to an oropharyngeal infection. Recently, several cases following a primary infection site other than the oropharynx have been reported as atypical Lemierre's syndrome; although, these primary lesions are limited to the head and neck. This is the first case potentially sequential to infectious foci outside the head and neck., Case Presentation: We describe an atypical Lemierre's syndrome in a 72-year-old woman with rheumatoid arthritis, which occurred during the treatment of Streptococcus anginosus bacteremia acquired from a sacral ulcer infection related to rheumatoid vasculitis. At first, the symptoms resolved after the initial administration of vancomycin for the bacteremia caused by methicillin-resistant Staphylococcus aureus and Streptococcus anginosus that entered via a sacral ulcer. On the 8th day, the patient developed a fever of 40 °C and unexpectedly required 10 L of oxygen due to rapid deterioration of oxygenation temporarily. Immediately contrast-enhanced computed tomography was performed to investigate systemic thrombosis including pulmonary embolism. Afterward, the newly formed thrombi at the right external jugular vein, bilateral internal jugular veins, and the right small saphenous vein were detected, and apixaban was started. On the 9th day, the patient again had an intermittent fever of 39.7 °C, and continuous Streptococcus anginosus bacteremia was revealed; subsequently, clindamycin was administered. On the 10th day, she developed a left hemothorax; consequently, apixaban was discontinued, and a thoracic drain was inserted. She repeatedly had an intermittent fever of 40.3 °C, and contrast-enhanced computed tomography detected an abscess formation at the left parotid gland, pterygoid muscle group, and masseter muscle. After Lemierre's syndrome was diagnosed in combination with the abovementioned jugular vein thrombus, clindamycin was replaced with meropenem, and vancomycin was increased. Swelling of the lower part of the left ear became prominent with delay and peaked at approximately the 16th day. The subsequent treatment course was favorable, and she was discharged on the 41st day., Conclusion: Clinicians should consider Lemierre's syndrome as the differential diagnosis of internal jugular vein thrombosis occurring during sepsis, even though an antibiotic is administered or a primary infection site is anything besides the oropharynx., (© 2023. The Author(s).)