Summary

• Clinical syndrome usually caused by Epstein Barr virus (EBV).
• Characterised by fever, pharyngitis, lymphadenopathy, and atypical lymphocytosis, in older children and young adults.
• Often sub-clinical in young children.
• Positive heterophile antibody test and serological test for antibodies against EBV are usually diagnostic.
• Rare but potentially life-threatening complications include severe upper airway obstruction, splenic rupture, fulminant hepatitis, encephalitis, severe thrombocytopenia, and haemolytic anaemia.
• Treatment is usually symptomatic.