Can West Nile virus (WNV) cause pancytopenia?

West Nile Virus and Pancytopenia

West Nile virus (WNV) infection is not typically associated with pancytopenia as a primary manifestation, though it may occur in severe cases, particularly in immunocompromised patients.

Hematological Manifestations of WNV

West Nile virus primarily causes neurological manifestations when it becomes invasive, but hematological findings can occur in some cases:

• The most common clinical laboratory findings in WNV infection include:

  • Moderately elevated white blood cell count
  • Mild anemia
  • Hyponatremia 1

• Other laboratory findings that may be present:

  • Thrombocytopenia (low platelets)
  • Elevated hepatic enzymes 1

• In the cerebrospinal fluid (CSF), WNV typically causes:

  • Lymphocytic pleocytosis
  • Moderately elevated protein levels 1

Special Populations at Risk

Certain patient populations may be more susceptible to developing severe manifestations of WNV infection, including potential hematological complications:

Immunocompromised Patients

• Bone marrow transplant recipients may develop severe, potentially fatal WNV infections with atypical presentations 2
• In immunocompromised patients, standard serological testing may be negative despite active infection 2
• Nucleic acid amplification testing (NAAT) is more sensitive in immunocompromised patients due to prolonged viremia 3

Solid Organ Transplant Recipients

• Renal transplant recipients on immunosuppressive therapy may develop severe WNV infections 4
• Recurrent WNV infections have been reported in transplant patients, requiring modification of immunosuppressive regimens 4

Diagnostic Considerations

When evaluating for WNV in a patient with pancytopenia:

1. Consider WNV in patients with unexplained fever or neurological symptoms during summer and fall months 3, 5
2. First-line testing includes:
   • Serum WNV-specific IgM antibodies
   • CSF WNV-specific IgM antibodies (for suspected neuroinvasive disease) 3
3. In immunocompromised patients:
   • Lower threshold for testing should be considered
   • NAAT testing should be performed even if serology is negative 3, 2

Clinical Implications

• While pancytopenia is not a classic feature of WNV infection, clinicians should be vigilant for hematological abnormalities in:

  • Elderly patients (≥70 years)
  • Patients with hematologic malignancies
  • Solid organ transplant recipients
  • Patients receiving B-cell-depleting monoclonal antibodies 5

• These populations have higher mortality rates (20-40%) with WNV neuroinvasive disease 5

Management Considerations

There are no specific antiviral treatments for WNV infection. Management focuses on:

• Supportive care
• In transplant recipients with severe WNV infection, consider:
  • De-escalation of immunosuppressive drugs
  • Intravenous immunoglobulin (400 mg/kg/day for 7 days) has been used in some cases 4

Prevention

Since there is no specific treatment for WNV infection, prevention is crucial:

• Personal protective measures against mosquito bites
• Community mosquito control interventions
• Screening of blood and organ donors in endemic areas 5

In conclusion, while pancytopenia is not a hallmark feature of WNV infection, it may occur in severe cases, particularly in immunocompromised hosts. Clinicians should maintain a high index of suspicion for WNV in patients presenting with unexplained hematological abnormalities during mosquito season, especially in endemic areas.