Epstein-Barr virus (EBV) infectious mononucleosis

Overview

•Classic triad: fever, exudative pharyngitis/tonsillitis, cervical lymphadenopathy (classically posterior chain)

•Palatal petechiae - at hard/soft palate junction; highly suggestive of EBV IM

•Splenomegaly - up to 50-75% of cases; peaks second week; creates rupture risk

•Fatigue - profound; can persist weeks to months

•Maculopapular rash - occurs in ~5-15% spontaneously; rises to >90% if amoxicillin or ampicillin given

⚠️

The amoxicillin/ampicillin rash in EBV is NOT a true penicillin allergy - it is immune complex-mediated in the context of EBV B cell activation. Do NOT document as penicillin allergy; do NOT avoid penicillins in future.

Investigations

•FBC - atypical lymphocytosis (>10% atypical lymphocytes = reactive CD8+ T cells, NOT infected B cells); mild thrombocytopaenia

•Monospot test (heterophile antibody test) - first-line; sensitivity ~85% in adults, lower in children <12 and in first week

•EBV-specific serology (VCA IgM/IgG, EBNA IgG) - gold standard; VCA IgM positive in acute primary infection; use when Monospot negative

•LFTs - elevated transaminases in ~80%; usually self-limiting

Management

🥇 First-line

•paracetamol or ibuprofen for fever/pain; encourage oral hydration and rest

•Avoid amoxicillin and ampicillin - use phenoxymethylpenicillin if bacterial superinfection confirmed

•Contact sport and strenuous activity avoidance - at least 4 weeks from symptom onset to reduce splenic rupture risk

🥈 Second-line

•short course prednisolone - for severe tonsillar swelling causing airway compromise; not routine

📌

No antiviral therapy has proven clinical benefit in immunocompetent patients with typical EBV IM - management is supportive.

Complications

•Splenic rupture - most feared; lymphocytic infiltration causes capsular fragility; may be spontaneous or post-trauma; left upper quadrant pain radiating to shoulder tip; surgical emergency

•Haematological - haemolytic anaemia (autoimmune, cold-agglutinin mediated), thrombocytopaenia; iron-deficiency anaemia is NOT a direct complication

•Airway obstruction - massive tonsillar/pharyngeal oedema; may need corticosteroids or emergency airway intervention

•Neurological - rare: encephalitis, meningitis, Guillain-Barré, Bell's palsy; encephalitis is NOT a common complication of EBV (HSV is the classic cause of encephalitis)

•Oncogenic associations (long-term) - Burkitt lymphoma, Hodgkin lymphoma (EBV in Reed-Sternberg cells ~50%), nasopharyngeal carcinoma

🚨

Red flags requiring emergency admission: stridor/respiratory distress (airway obstruction), sudden severe left upper quadrant pain or haemodynamic instability (suspect splenic rupture), signs of meningism or altered consciousness, severe dehydration.