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Infectious Mononucleosis

Cause

Infectious mononucleosis (IMN) is caused by infection with Ebstein Barr virus (EBV). This virus enters through the pharyngeal epithelium and replicates in B-lymphocytes causing them to proliferate. Atypcial mononuclear cells appear in the blood and represent T-lymphocytes reacting to the presence of infected B-lymphocytes. The virus maintains a low level of replication throughout life. The spleen and lymph nodes become intensely infiltrated with mononuclear cells.

EBV is transmitted by saliva and droplet infection (airborne) with an incubation period of 2 weeks.

Symptoms and clinical picture of mononucleosis

The disease most commonly occurs in young adults and presents with fever, headache, sore throat. Pharyngitis, often the most prominent sign, can be accompanied by enlargement of the tonsils with an exudate resembling that of streptococcal pharyngitis. Petechiae (tiny bleeding spots) may occur in the soft palate.

A generalized lymph gland enlargement (particularly involving the posterior neck lymph glands) and an enlargement of the spleen are common. They are tender, symmetric but not fixed in place. Mild hepatitis is common.

A morbilliform or papular rash, usually on the arms or trunk, develops in about 5% of cases. Most patients treated with ampicillin develop a macular rash. Erythema nodosum and erythema multiforme have also been described.

Other diseases related to EBV infection

  • Burkitt's lymphoma
  • Nasopharyngeal carcinoma
  • X-linked combined variable immunodeficiency
  • Lymphoid interstitial pneumonia in children with AIDS.

Diagnosis of mononucleosis

Atypical lymphocytes are seen in the blood film. Paul ? Bunnel and monospot tests are used to detect heterophil antibodies and are usually positive by the second week. Specific EBV IgM antibodies indicate a recent infection by the virus.

Treatment of mononucleosis

The disease may resolve alone in healthy subjects. Steroids (prednisolone) is advised when the condition is prolonged or accompanied by complications.

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