Lemierre syndrome is a rare and potentially life-threatening complication of bacterial infections that usually affects previously-healthy adolescents and young adults. It most commonly develops in association with a bacterial throat infection, but it may develop in association with an infection involving the ears, salivary glands (parotitis), sinuses, or teeth; or in association with an Epstein-Barr infection. The bacteria typically responsible for infection in Lemierre syndrome is Fusobacterium necrophorum, although a variety of bacteria can be responsible. In people with Lemierre syndrome, the initial infection spreads into tissues and deep spaces within the neck, leading to the formation of an infected blot clot (septic thrombophlebitis), sometimes made up of pus, in the internal jugular vein (the blood vessel that carries blood away from the brain, face, and neck). In addition to worsening symptoms of the initial infection, symptoms at this stage of the disease typically include persistent fever and chills (rigors), as well as pain, tenderness and swelling of the throat and neck. The infected clot then circulates in the blood (septicemia), resulting in the infection also spreading to the lungs (most commonly), skeletal system, and/or other parts of the body such as the spleen, liver, kidney, heart, or brain. This can lead to life-threatening complications such as respiratory distress syndrome due to pulmonary emboli (blood clots in the lung), damage to other affected organs, and/or septic shock (in about 7% of cases). Lemierre syndrome may be diagnosed based on signs and symptoms, various blood tests, and imaging studies. Because most throat infections in young, healthy people do not cause severe health problems, diagnosis and treatment may be delayed. The main treatment involves intravenous antibiotic therapy over several weeks, but surgery may be necessary when there is abscess formation, respiratory distress, or severe clotting in the chest or brain. The long-term outlook and chance of survival in people with Lemierre syndrome varies depending on how much the syndrome progresses, but even with appropriate treatment, it is fatal in some cases.

Lemierre syndrome most often results from a complication of a bacterial throat infection, but it has also been reported to result from infections involving other areas of the head and neck, including the ears, salivary glands (parotitis), sinuses, and teeth.  The bacteria most commonly responsible for Lemierre syndrome is Fusobacterium necrophorum (F. necrophorum). This bacteria is normally present in healthy people in various parts of the body (including the throat, digestive tract, and female genitals). The bacteria may cause invasive disease by releasing toxins into surrounding tissue. It has also been speculated that in some cases, other bacteria (or a virus) may be responsible for the initial infection prior to the onset of Lemierre syndrome, leading to conditions that favor the growth and invasion of F. necrophorum into surrounding tissues. Bacteria other than F. necrophorum that have been reported in case studies include Streptococcus species (“strep”), Bacteroides species, Staphylococcus aureus, and Klebsiella pneumoniae. The Epstein-Barr virus has also been reported in people prior to the onset of Lemierre syndrome.

Treatment recommendations for Lemierre syndrome primarily are based on clinical experience and in vitro studies and are supported by limited data from observational studies and case reports. The main components of treatment include intravenous antibiotic therapy and drainage at the sites of infection. A combination of antibiotics (at least one beta-lactamase resistant antibiotic and one beta-lactam antibiotic) is recommended to cover all possible responsible bacteria, as there have been case reports of treatment failure with single antibiotics (monotherapy). A combination is used because some bacteria produce an enzyme called beta-lactamase, which makes them resistant to beta-lactam antibiotics.  Ideally, the specific antibiotics used should depend on the culture results, when available. Antibiotic therapy typically is continued for up to 6 weeks in order to allow the medication to penetrate infected clots. Surgical incision and drainage of any abscesses may be needed to control the infection. Surgical removal of infected clots is generally reserved for cases in which antibiotic therapy and drainage are not effective. Surgical treatment may also be needed for breathing problems due to pulmonary emboli; severe blood clotting elsewhere in the body (particularly the brain); mediastinitis; or to remove dead, damaged, or infected tissue (debridement). The role of anticoagulation (the use of blood thinners) for blood clots in Lemierre syndrome is uncertain and has been controversial. While anticoagulation may help prevent new clots from forming and complications associated with thrombosis, it may cause a high risk of bleeding complications and/or aid the spread of infected material. Lemierre syndrome without evidence of extensive clotting typically resolves with appropriate antibiotic therapy and does not require anticoagulation. However, it may be recommended in severe or progressive cases with persistent sepsis, extensive clotting, clotting that extends to the cerebral sinuses, and/or when a patient does not begin to improve within 72 hours of appropriate antibiotic or surgical treatment.

Advanced Lemierre syndrome is a life-threatening condition. The current mortality (death due to the syndrome) is estimated to be between 5% and 18%, depending on the source of the data. However, as the mortality in the pre-antibiotic era reportedly was 90%, the outlook for people with Lemierre syndrome has improved significantly due to advances in antibiotic therapy and high-level intensive care. Receiving the diagnosis as quickly as possible and starting appropriate treatment increases the chance of survival. Severe complications of Lemierre syndrome may include osteomyelitis (bone infection), meningitis, acute respiratory distress syndrome, and septic shock.

Lemierre syndrome may be diagnosed based on signs and symptoms, as well as a variety of blood tests and imaging studies. Blood tests may reveal various abnormalities suggestive of the diagnosis, such as a high white blood cell count, low blood platelet count (or other evidence of clotting problems), and abnormal kidney and/or liver function. Blood cultures should be collected, and the results commonly indicate that the blood is infected with the F. necrophorum bacteria, which often prompts a high suspicion for Lemierre syndrome. In some cases, blood cultures are negative due to difficulties that can be associated with culturing anaerobic bacteria. Imaging studies may include a chest X-ray, which may detect septic emboli, abscesses, or other lung complications. Imaging studies to specifically evaluate septic thrombosis of the internal jugular vein may include ultrasound, CT scan of the neck with contrast, and magnetic resonance imaging (MRI). Magnetic resonance venography (MRV) has the highest sensitivity for detecting internal jugular thrombosis.