CLINICAL

• 1-yr incidence ranges from 1.7% with asymptomatic HIV to 3.1% with CD4-define AIDS to 8.7% with AIDS-defining illness.
• Increased risk with decreasing CD4, injection drug use, African-American race, anemia. Other causes include alcohol abuse, sulfonamides, thiazides, folate and vitamin B₁₂ deficiency, IV cocaine, and liver cirrhosis / portal hypertension.
• Direct effects of HIV on hematopoietic progenitors and idiopathic thrombocytopenic purpura (ITP) are major causes. In the latter, production of autoantibodies against certain platelet antigens (PA-IgG) leads to antibody-coated platelets removed by macrophages in the spleen.
• Increased risk of bleeding with PLT < 10,000-20,000.
• Heparin-induced thrombocytopenia may be more common in HIV-infected than uninfected.
• Uncommon with current ART (1-3% with plt < 50,000); more common if uncontrolled HIV replication and with viral hepatitis coinfection