What clinical features should I consider when diagnosing glandular fever in a young adult?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 16 August 2025Updated: 16 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

When diagnosing glandular fever (infectious mononucleosis) in a young adult, several clinical features should be considered. The illness typically presents with symptoms that usually last for 2–4 weeks ,.

Key clinical features include:
  • Fever, which may be unexplained .
  • Sore throat, which can present with extreme tonsillar hypertrophy ,.
  • Lymphadenopathy, often unexplained and potentially generalised .
  • Fatigue, which can be persistent .
  • Splenomegaly, which may be unexplained .

It is important to be aware of features that may indicate a serious complication or require urgent medical review ,:

  • Signs of upper airway obstruction, such as stridor and respiratory distress ,.
  • Signs of severe dehydration or difficulty swallowing fluids ,.
  • Severe systemic illness ,.
  • Acute upper abdominal pain, which could indicate acute hepatitis or splenic rupture ,.

Additionally, some clinical features of glandular fever, such as unexplained fever, lymphadenopathy, splenomegaly, persistent fatigue, night sweats, pruritus, or weight loss, can overlap with symptoms of other serious conditions like leukaemia or lymphoma, particularly in young people aged 16 to 24 . Therefore, a comprehensive assessment is crucial to differentiate glandular fever from other potential diagnoses . The management recommendations for infectious mononucleosis are based on UK Health Security Agency (UKHSA) guidance and expert opinion from various review articles ,. For instance, extreme tonsillar hypertrophy and dehydration may necessitate hospital admission for observation and possible intravenous fluid therapy ,. The natural course of the illness, with most symptoms lasting 2–4 weeks, is also based on expert opinion ,.

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