AKT · Infections/Viral infectionslow yield

Infectious mononucleosis (EBV & CMV)

Epstein-Barr virus (commonest) — 'glandular fever'; CMV/toxoplasma give a similar picture

Overview

A clinical syndrome ('glandular fever'), usually from Epstein-Barr virus, of fever, exudative pharyngitis and lymphadenopathy in adolescents/young adults, with atypical lymphocytes and a positive heterophile-antibody (Monospot/Paul-Bunnell) test. CMV and toxoplasmosis cause a Monospot-negative mononucleosis-like illness. Two high-yield traps: a maculopapular rash if amoxicillin/ampicillin is given, and splenic rupture risk — so avoid contact sports.

Recognise

Fever, marked exudative tonsillitis/pharyngitis, tender cervical (often posterior) lymphadenopathy, malaise/fatigue; palatal petechiae, hepatosplenomegaly, periorbital oedema
Blood: atypical lymphocytes (reactive); positive heterophile-antibody (Monospot/Paul-Bunnell); deranged LFTs common; EBV serology confirms
Classic traps: widespread maculopapular RASH after amoxicillin/ampicillin; SPLENOMEGALY → risk of splenic rupture (avoid contact sport for ~4–6 weeks)

Red flags

Splenic rupture (sudden abdominal pain/shock after minor trauma) → emergency
Airway compromise from gross tonsillar enlargement → corticosteroids/airway management

Differentials & how to tell them apart

Streptococcal tonsillitisCentor/FeverPAIN; but giving amoxicillin in EBV causes a rash — confirm before treating presumptively

CMV / toxoplasmosis mononucleosisMonospot-NEGATIVE mononucleosis-like illness; serology distinguishes

Acute HIV seroconversionmononucleosis-like illness with risk factors — test for HIV

Leukaemia/lymphomapersistent/atypical — blood film/marrow

Investigations

FBC + blood film (atypical lymphocytes), heterophile-antibody (Monospot/Paul-Bunnell — may be negative early or in young children), EBV serology (VCA IgM); LFTs (often raised); if Monospot-negative consider CMV/toxoplasmosis/acute HIV.

Management

Supportive care; avoid amoxicillin (rash) and contact sport (splenic rupture)

1Recognise the triad (fever + exudative pharyngitis + lymphadenopathy) with atypical lymphocytes and a positive Monospot; treat supportively (self-limiting).Gate: AVOID amoxicillin/ampicillin (causes a widespread maculopapular rash in EBV) and advise NO contact sport for ~4–6 weeks (splenic rupture risk). Monospot-negative → consider CMV/toxoplasmosis/acute HIV.
2Corticosteroids only for complications (airway obstruction, severe cytopenias); manage splenic rupture as an emergency; test for HIV if the picture/risk fits.

Supportive care (rest, fluids, analgesia/antipyretics) — self-limiting; AVOID amoxicillin/ampicillin (rash); avoid contact sport ~4–6 weeks (splenic rupture)

Corticosteroids only for complications — e.g. airway compromise from tonsillar enlargement, severe haemolysis/thrombocytopenia

Treat the specific cause if not EBV — CMV/toxoplasmosis usually supportive in the immunocompetent; consider HIV

Safety-net for splenic rupture — warn re abdominal pain/sport

Key points

Adolescent + fever + exudative tonsillitis + posterior cervical lymphadenopathy + atypical lymphocytes + positive Monospot = EBV glandular fever → supportive. Two traps: amoxicillin → maculopapular RASH; splenomegaly → SPLENIC RUPTURE (no contact sport 4–6 wks). Monospot-negative → CMV/toxoplasmosis/acute HIV. (Also carded on ENT.)

Monitor & prognosis

Symptom resolution (fatigue may persist), splenomegaly/sport advice, LFTs; complications.

Self-limiting over weeks; fatigue can linger; complications are uncommon.

Source: NICE CKS (glandular fever); cross-ref ENT, sexual_health (HIV)