• Clinical science

Infectious mononucleosis (Kissing disease)

Summary

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).

Epidemiology

  • 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

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

  • Pathogen: Epstein-Barr virus (EBV), also called human herpes virus 4 (HHV-4)
  • Transmission: : Infectious mononucleosis is highly contagious and spreads via bodily secretions, especially saliva; → "kissing disease"

References:[1]

Pathophysiology

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

References:[2][3]

Clinical features

Splenomegaly can lead to a potentially life-threatening splenic rupture!

References:[3][4][5][6][7][8]

Diagnostics

Clinical suspicion of IM is confirmed via antibody testing.

References: [3][5]

Pathology

Histopathology of lymph nodes

  • 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.

References:[9][10][11][12]

Differential diagnoses

References:[3][13]

The differential diagnoses listed here are not exhaustive.

Treatment

Symptomatic therapy

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!

References:[5]

Complications

Immunocompromised patients are more prone to complications.

Nervous system
Hematological system

Other organs

Associated malignancies

References:[5][14][15]

We list the most important complications. The selection is not exhaustive.