Infectious mononucleosis, also known as glandular fever, mono or kissing disease. It is an infectious disease primarily caused by Epstein-Barr Virus (human herpes virus 4) in 90% of the cases, but can also be caused by CMV (human herpes virus 5) or HHV-6.
Pathophysiology
EBV is found in the saliva of infected individuals. It may be spread by kissing, sharing cups, toothbrushes or other mechanisms of salivary transfer. It may also be spread by blood, semen and bodily fluids. It is similar to HSV in that it cannot be completely removed, and lays dormant in most people. The disease may be infectious several weeks prior to symptoms.
It has both latent and lytic life cycles:
- Lytic - this makes up the early primary infection. It potentially occurs in oropharyngeal B-cells. EBV enters these cells via the tonsillar crypts. The B-cells then circulate and spread infection to the spleen, liver and peripheral lymph nodes → immune responses (both humoral and cellular responses). Symptoms may arise from a hyperactivated immune response as opposed to the infection itself (more research is needed to confirm this).
- Latent - latent infection is established as it lays dormant in infected lymphocytes. There are low levels of replication. The disease may lay dormant for years before reactivation.
😷 Presentation
There is a classic triad of infectious mononucleosis/glandular fever:
- Fever
- Pharyngitis - sore throat.
- Lymphadenopathy - lymph nodes in both the anterior and posterior chain are affected
Other symptoms may include:
- Fatigue - patients often return with chronic fatigue after a previous viral infection.
- Tonsillar enlargement
- Splenomegaly
- Maculopapular rash when given amoxicillin or cephalosporins
🔍 Investigations
NICE recommends an FBC and monospot test in the 2nd week of illness to confirm diagnosis:
- FBC - shows lymphocytosis.
- Monospot test (heterophile antibody test) - positive. If it is negative, the test should be repeated in 5-7 days.
Other tests include:
- EBV antibodies
- IgM antibody - suggests acute infection.
- IgG antibody - persists after infection, suggesting immunity.
- EBV viral serology - can be used if the patient is <12 years old, immunocompromised, or if the repeat monospot test remains negative, but clinical suspicion remains high.
- Abdominal ultrasound - may show splenomegaly.
In infectious mononucleosis, the body produces heterophile antibodies - these are antibodies that are multipurpose and not specific to solely EBV. It takes up to 6 weeks for these antibodies to be produced.
They can be tested for using:
- Monospot test - introduces patient’s blood to RBCs from horses. If heterophile antibodies are present, they will react to the horse RBC → positive result.
- Paul-Bunnell test - similar to the monospot test, but uses RBCs from sheep.
They are almost 100% specific for infectious mononucleosis, however, not all patients with infectious mononucleosis produce heterophile antibodies and it can take up to 6 weeks for them to be produced.
🧰 Management
It is self-limiting (2-4 weeks) so management is conservative:
- Rest and hydration
- Avoid alcohol - as liver function is already impaired with the disease.
- Analgesia
- Avoid contact sports - due to risk of splenic trauma
- Avoid ampicillin, amoxicillin, cephalosporins
🚨 Complications
- Splenic rupture
- Glomerulonephritis
- Haemolytic anaemia
- Thrombocytopenia
- Chronic fatigue
- Burkitt’s lymphoma