- Clinical science
Infectious mononucleosis (IM), also called "mono" or the "kissing disease", is an acute condition caused by the Epstein-Barr virus (EBV). The disease is highly contagious and spreads via bodily secretions, especially saliva. Infection frequently goes unnoticed in children; mainly adolescents and young adults exhibit symptoms. Symptomatic individuals typically first experience fever, malaise, and fatigue, which is later accompanied by acute pharyngitis, tonsillitis, lymphadenopathy, and/or splenomegaly lasting up to a month. IM is also sometimes associated with a measles-like exanthem, especially in individuals who are falsely diagnosed with bacterial tonsillitis and given ampicillin or amoxicillin. To avoid misdiagnosis, suspected cases are confirmed with a heterophile antibody test (monospot test), or in some cases, positive serology. Patients exhibit lymphocytosis, often with atypical T lymphocytes on a peripheral smear. IM is treated symptomatically, as it is usually self-limiting. Although complications are rare, IM is associated with atraumatic splenic rupture due to splenomegaly and multiple malignancies (e.g., Hodgkin's lymphoma, Burkitt lymphoma).
- Approx. 90–95% of adults are EBV-seropositive worldwide.
- Peak incidence: of symptomatic disease: 15–24 years
- Incidence: 500/100,000 per year in the US
Epidemiological data refers to the US, unless otherwise specified.
EBV infects B lymphocytes in mucosal epithelium (e.g., oropharynx, cervix) via the CD21 receptor; → infected B lymphocytes induce a humoral (B-cell) as well as a cellular (T-cell) immune response → an increased concentration of “atypical” lymphocytes in the bloodstream, which are CD8+ cytotoxic T cells that fight infected B lymphocytes
- Incubation period: 4–8 weeks
- Symptoms typically occur in adolescents and young adults and last for 2–4 weeks.
- Young children are often asymptomatic.
- Splenomegaly (50% of cases), fever, fatigue, malaise
- Pharyngitis and/or tonsillitis (reddened, enlarged tonsils covered in pus); palatal petechiae
- Bilateral cervical lymphadenopathy (especially posterior) that may become generalized and can, in severe cases, lead to airway obstruction
- Abdominal pain
- Possibly hepatomegaly and jaundice
- Maculopapular rash; (similar to measles): caused by the infection itself in about 5% of cases, but is generally associated with the administration of aminopenicillin (e.g., ampicillin or amoxicillin)
Clinical suspicion of IM is confirmed via antibody testing.
- Monospot test: detects heterophile antibodies produced in response to EBV infection using RBCs from horses; specificity of ∼ 100%, sensitivity of 85%
- Laboratory analysis: elevated LDH and liver transaminases
- Peripheral smear: lymphocytosis with > 10% atypical lymphocytes (in some cases, up to 90%)
- Serology: : indicated if IM is suspected but a monospot test is negative
- Reactive follicular hyperplasia due to increased activation of B lymphocytes
- Paracortical expansion through numerous, large immunoblasts (B and T cells), later expanding throughout the entire node
- Atypical Reed-Sternberg-like cells may be observed, which is why the disease is sometimes mistaken for Hodgkin's disease.
- Avoid physical activity that may trigger splenic rupture (e.g., contact sports) for at least 3 weeks after the onset of symptoms.
- Fluids (IV administration if necessary)
- Analgesics/antipyretics (e.g., acetaminophen)
Tonsillitis is an important differential diagnosis that is often treated with aminopenicillins (e.g., ampicillin). However, if given to a patient with IM, the patient often develops a macular erythematous rash after 5–9 days!
Immunocompromised patients are more prone to complications.
|Associated malignancies|| |
We list the most important complications. The selection is not exhaustive.