A 56-year-old female patient presented with a 3-day-old odynophagy and a painful swelling in the left side of the neck. In addition to reddening and swelling of the left side of the neck, which was painful on palpation, leukocytosis and increased C-reactive protein (CRP) and fibrinogen levels were also found. Enlarged lymph nodes along the left vessel-nerve sheath and thrombosis of the internal jugular vein were detected by sonography and computed tomography. The patient could be identified as a heterozygote carrier of the factor V Leiden mutation. This mutation has a thrombotic characteristic due to resistance to activated protein C (APC). Subacute lymphadenitis was an additional disruptive factor and led to thrombosis in the internal jugular vein. The patient received antibiotic treatment and Marcumar, which is planned to be given for a 3-month period.