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Infectious mononucleosis

Author: Dr Sarah Hill, Dermatology Registrar, Waikato Hospital, Hamilton, New Zealand, 2007.

Infectious mononucleosis — codes and concepts

What is infectious mononucleosis?

Infectious mononucleosis is also known as ‘glandular fever’. It typically affects young adults aged 15 to 25 years. Infectious mononucleosis is caused by human herpes virus type 4, more often known as Epstein–Barr virus (EBV). This virus is passed from person to person by saliva such as sharing a glass or kissing. The incubation period from contact until symptoms is 1 to 2 months.

What are the clinical features of infectious mononucleosis?

The most common presentation of infectious mononucleosis is with a fever, enlarged lymph nodes and a sore throat. However the virus can also affect other organs, as shown in the table below.

Organ involvedSymptoms and signs
  • Splenomegaly (an enlarged spleen)
  • Arthritis in one or more joints
  • Glomerulonephritis
Nervous system
  • Meningoencephalitis
  • Bell's palsy (facial palsy)
  • Transverse myelitis
  • Guillain–Barré syndrome
Gastrointestinal tract
  • Hepatitis
  • Interstitial pneumonia
  • Pericarditis
  • Eyelid swelling
  • Keratitis
  • Uveitis
  • Conjunctivitis
  • Retinitis
Blood system
  • Autoimmune haemolytic anaemia (breakdown of red cells)
  • Thrombocytopenia (reduced platelet count)
  • Neutropaenia (reduced white cell count)
  • Cold agglutinins (proteins that precipitate in cooler conditions)
  • Immunodeficiency

Involvement of the skin by infectious mononucleosis

Involvement of the skin is seen in about 10% of non-hospitalised patients with infectious mononucleosis. Most commonly, there is a faint, widespread, non-itchy rash, which lasts for about a week. It is described as maculopapular exanthem, i.e. there are flat patches that may contain small bumpy red spots. It thought to be directly due to the virus. This rash often appears on the trunk and upper arms first, and a few days later extends to involve the face and forearms. Other appearances of this rash include:

  • Morbilliform (small, flat, measles-like patches)
  • Papular (small bumps)
  • Scarlatiniform (tiny spots like scarlet fever)
  • Vesicular (little blisters)
  • Purpuric (bruise-like)

This is in contrast to a more intense itchy maculopapular or morbilliform rash which appears on extensor surfaces and pressure points 7 to 10 days after treatment with beta-lactam antibiotics such as ampicillin, amoxicillin and cephalosporins. This rash indicates a ‘hypersensitivity reaction’ to the antibiotic. It is not a true allergy and does not occur if the antibiotic is given later on in the absence of EBV infection.

Skin signs of EBV infection

There are a variety of uncommon skin conditions associated with EBV infection, including:

How is the diagnosis of infectious mononucleosis made?

Usually a blood test is taken, which detects characteristic atypical lymphocytes (white blood cells). A positive 'monospot' screening test may be requested, as there are several other viral infections that may cause similar symptoms in which atypical lymphocytes are detected.

Liver function is usually checked. Other tests will depend on what organs are affected by the infection.

Other more sensitive and specific blood tests are generally only done in acute EBV infection with atypical features. These include: antibodies to EBV capsid and nuclear antigen, and polymerase chain reaction assay for EBV DNA.

What treatment is available for infectious mononucleosis?

Treatment may require bed rest and simple analgesia such as paracetamol during the febrile stage. Aciclovir is sometimes prescribed but it is not very effective. Antibiotics are not helpful.

Recovery is generally complete, but it can take several weeks to months to feel quite well again. Prolonged tiredness is common.

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