Cytomegalovirus

Definition

• Human herpesvirus (DNA virus) transferred by respiratory droplets and blood transfusions that lies dormant in white blood cells

Epidemiology

• 80% of people are CMV-IgG positive

Risk Factors

• Crowding

Presentation

• Asymptomatic when young
• Mono-like or influenza-like illness when older

Investigations

• CBC showing leukopenia or pancytopenia
• Mild elevation in liver enzymes
• CMV-IgG positive
• Detectable CMV DNA in peripheral blood, though it can rise during intercurrent illness

Management

• First-line: valganciclovir or ganciclovir
  • Measure baseline CBC first
• Second-line, if cytopenias: foscarnet
• Third-line: cidofovir, marabavir
• At McMaster, expect 1-log drop within 2 weeks (lab-dependent)

Prophylaxis

• Solid-organ transplant
  • Donor+/Recipient– high risk for reactivation, the the donor organ infecting the recipient
  • Donor–/Recipient+ intermediate risk
  • Donor+/Recipient+ intermediate risk
  • Donor–/Recipient– lowest risk
  • High and intermediate risk patients get prophylaxis with valganciclovir for some amount of duration...
• Hematologic stem cell transplant
  • Donor+/Recipient+ high risk for reactivation
  • Donor–/Recipient+ high risk
  • Donor+/Recipient– intermediate risk
  • Donor–/Recipient– lowest risk
  • Preemptive monitoring with weekly CMV DNA PCR starting week 2
• Treat if greater than threshold (1425 at McMaster) or if rising titre with symptoms

Complications

• Even when dormant, can cause mild immunosuppression that predisposes to fungal infections
• Asymptomatic shedding in lungs during intercurrent illness
• Viremia with influenza-like illness
• End-orgam damage
  • CMV colitis
  • Retinitis in AIDS patient (CD4 < 50-100)
  • Organ inflammation of solid-organ transplants
  • Pneumonitis in stem cell transplants

Resistance

• Inherent acyclovir resistance
• Tyrosine kinase mutation UL97? confers resistance to (val)ganciclovir
• Polymerase mutation U54? confers resistance to (val)ganciclovir and foscarnet
• Consider resistance if CMV DNA titres not decreasing despite appropriate treatment
• Resistance genotyping available