What are the viral causes of thrombocytopenia?

Viral Causes of Thrombocytopenia

The major viral causes of thrombocytopenia include HIV, hepatitis C virus (HCV), cytomegalovirus (CMV), varicella zoster virus, and parvovirus B19, with treatment of the underlying viral infection often resulting in resolution of thrombocytopenia. 1, 2

Common Viral Etiologies

• HIV infection is a well-established cause of thrombocytopenia that may occur years before other symptoms develop, with routine serologic testing recommended in all adults with suspected thrombocytopenia 1
• Hepatitis C virus (HCV) can cause thrombocytopenia even without overt liver disease, and should be screened for in all adult patients with suspected immune thrombocytopenia 1, 3
• Cytomegalovirus (CMV) can produce thrombocytopenia through bone marrow suppression and immune-mediated mechanisms 1, 2
• Varicella zoster virus is associated with transient thrombocytopenia during acute infection 1, 2
• Parvovirus B19 can cause persistent thrombocytopenia through direct effects on megakaryocytes 1, 4
• Dengue virus is a common cause of febrile thrombocytopenia, particularly in endemic regions during monsoon seasons 5, 6
• Measles virus can trigger thrombocytopenia through multiple mechanisms including bone marrow suppression 4
• Live attenuated virus vaccines have been associated with transient thrombocytopenia in some cases 1

Pathophysiological Mechanisms

• Viral infections can cause thrombocytopenia through multiple mechanisms:
  • Direct bone marrow suppression affecting megakaryocyte function 7, 6
  • Immune-mediated destruction of platelets through molecular mimicry 2, 4
  • Increased splenic sequestration of platelets 6, 3
  • Direct viral damage to endothelial cells leading to increased platelet consumption 2, 4
  • Development of autoantibodies against platelet glycoproteins 8, 3

Diagnostic Approach

• Complete blood count with peripheral blood smear examination is essential to confirm true thrombocytopenia and assess for other cytopenias 7
• Routine serologic testing for HIV and HCV is recommended in all adult patients with suspected immune thrombocytopenia, regardless of risk factors 1
• Testing for other viral infections should be guided by clinical presentation, including:
  • CMV serology or PCR in patients with mononucleosis-like symptoms 1, 2
  • Dengue testing in patients with fever and thrombocytopenia in endemic regions 5, 6
  • Parvovirus B19 testing in patients with concurrent anemia 2, 4

Management Principles

• HIV-associated thrombocytopenia: Treatment with antiretroviral therapy should be the first approach unless significant bleeding is present 1, 3
• HCV-associated thrombocytopenia: Consider antiviral therapy, though platelet counts should be monitored closely due to potential worsening with interferon-based regimens 1, 8
• For acute viral infections: Thrombocytopenia is often transient and resolves with treatment of the underlying infection 5, 6
• For severe thrombocytopenia with bleeding: Initial treatment may include corticosteroids, IVIg, or anti-D immunoglobulin while addressing the underlying viral cause 1

Clinical Pearls and Pitfalls

• Thrombocytopenia may be the presenting feature of HIV or HCV infection, appearing years before other symptoms develop 1, 3
• The degree of thrombocytopenia does not always correlate with bleeding risk; mortality is more often associated with multiorgan dysfunction than with the platelet count itself 5, 6
• In patients with persistent unexplained thrombocytopenia, consider screening for less common viral etiologies based on epidemiological risk factors 2, 4
• Spontaneous bleeding typically occurs when platelet counts fall below 20,000/μL, while petechiae and purpura are more common at counts below 50,000/μL 5