Cytomegalovirus (CMV) mononucleosis

Overview

CMV mononucleosis by immune status
FeatureImmunocompetent adultImmunocompromised (transplant/HIV)Congenital CMV
Key symptomsProlonged fever (>2 weeks), malaise, mild pharyngitis, lymphadenopathyCMV pneumonitis (dry cough, dyspnoea, bilateral infiltrates), hepatitis, colitis, retinitisMicrocephaly, petechial rash, hepatosplenomegaly, jaundice, low birth weight, seizures
TimingPrimary infection young adults4-12 weeks post-transplant (peaks when immunosuppression maximal)Symptomatic in ~10-15% at birth; ~85-90% asymptomatic at birth
Key long-term sequelaSelf-limitingMorbidity/mortality from end-organ diseaseSensorineural hearing loss - most common; can be progressive even if asymptomatic at birth

Feature	Immunocompetent adult	Immunocompromised (transplant/HIV)	Congenital CMV
Key symptoms	Prolonged fever (>2 weeks), malaise, mild pharyngitis, lymphadenopathy	CMV pneumonitis (dry cough, dyspnoea, bilateral infiltrates), hepatitis, colitis, retinitis	Microcephaly, petechial rash, hepatosplenomegaly, jaundice, low birth weight, seizures
Timing	Primary infection young adults	4-12 weeks post-transplant (peaks when immunosuppression maximal)	Symptomatic in ~10-15% at birth; ~85-90% asymptomatic at birth
Key long-term sequela	Self-limiting	Morbidity/mortality from end-organ disease	Sensorineural hearing loss - most common; can be progressive even if asymptomatic at birth

🎯
Highest-risk transplant scenario: CMV-seronegative recipient receiving organ from CMV-seropositive donor (D+/R-). CMV disease classically emerges 4-12 weeks post-transplant.

Investigations

•FBC - lymphocytosis with atypical lymphocytes; leucopenia and thrombocytopenia in immunocompromised

•LFTs - transaminitis (elevated ALT/AST); bilirubin may be raised

•Monospot (heterophile antibody test) - negative in CMV; positive in EBV - key differentiator

•CMV serology (IgM/IgG) - CMV IgM = primary infection or recent reactivation; seroconversion confirms primary infection. Unreliable in immunocompromised (blunted antibody response)

•CXR/CT chest - bilateral interstitial infiltrates / ground-glass opacification in CMV pneumonitis

🏆 Gold standard

•CMV PCR (blood/plasma) - quantitative viral load; essential in immunocompromised for diagnosis, monitoring and guiding treatment. Urine PCR used for congenital CMV in neonates

💡
In a transplant patient with fever and end-organ symptoms, always send CMV PCR viral load - this guides both diagnosis and treatment decisions. Do not rely on serology.

Management

•Immunocompetent (CMV mononucleosis): self-limiting - reassurance, rest, paracetamol for fever/pain, avoid contact sports for 4-6 weeks (splenomegaly risk). No antiviral needed

•Immunocompromised (systemic CMV disease): IV ganciclovir - first-line for acute systemic CMV; discuss reduction of immunosuppressive regimen with transplant team

•Transplant prophylaxis (D+/R- high-risk): valganciclovir orally for 3-6 months post-transplant. Alternative: pre-emptive strategy - regular CMV PCR monitoring, treat only when viral load crosses threshold

⚠️
Valganciclovir is for systemic/transplant CMV. Reassurance is appropriate for CMV mononucleosis in an immunocompetent patient - do not confuse these scenarios in the exam.