Lemierre's Syndrome as a Sexually Transmitted Disease Due to Porphyromonas asaccharolytica Suspected to Be Caused by Pharyngitis Due to Mycoplasma pneumoniae and Epstein-Barr Virus.

Porphyromonas asaccharolytica rarely causes Lemierre's syndrome (LS), which is characterised by sepsis and thrombophlebitis of the internal jugular vein. An 18-year-old man presented with fever and a sore throat after sexual contact containing oral sex, and his blood sample was positive for atypical lymphocytes. Infectious mononucleosis was suspected initially. However, laboratory data showed elevated D-dimer and procalcitonin levels, and a computed tomography scan showed a thrombus in the internal jugular vein leading to the diagnosis of LS. The Mycoplasma pneumoniae (MP) IgM titre was 1:640 (normal, ≦1:40), and the Epstein-Barr nuclear antigen titre (taken 59 days after admission) was 1:10 (normal, <1:10). It was assumed that LS developed after infection with Epstein-Barr virus (EBV) and MP. LS should be suspected in young patients with fever and sore throat with a history of recent sexual contact. As pharyngitis was considered the cause of LS, evaluation of the preceding infection such as MP or EBV leading to pharyngitis should also be considered.