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September 2001
This 13-year-old HIV-infected girl had scattered petechiae and purpura on her extremities, suggesting the possibility of thrombocytopenia. Her physical examination otherwise was normal except for moderate splenomegaly. The complete blood count revealed a platelet count of 43,000 platelets/uL. Her CD4 lymphocyte count was 134 cells/uL.
Thrombocytopenia is commonly observed in HIV-infected children, especially those with CD4 lymphocyte counts less than 200 cells/uL. Thrombocytopenia can be the initial sign leading to the diagnosis of HIV infection. HIV-associated thrombocytopenia is most commonly caused by an immune mediated platelet destruction. However, other causes of thrombocytopenia should be considered, including adverse drug reaction (e.g., trimethoprim-sulfamethoxazole, ganciclovir, fluconazole), thrombotic thrombocytopenic prupura (TTP), hypersplenism, or bone marrow infiltration with tumor or an opportunistic infection. Opportunistic infections associated with thrombocytopenia include histoplasmosis, cryptococcosis, and bacillary angiomatosis.
The pathogenesis of HIV-associated thrombocytopenia is enhanced destruction of platelets by the reticuloendothelial system, as well as decreased platelet production. HIV-infected thrombocytopenic patients often have increased amounts of platelet-associated IgG, IgM, C3, and C4.
If the HIV-infected child has a platelet count of 50,000/uL or greater and is asymptomatic, intervention generally is not necessary. Antiretroviral treatment, particularly with zidovudine, has been shown to improve HIV-associated thrombocytopenia. If acute intervention is required (platelet count less than 20,000/uL or symptomatic), IVIG has been shown to be effective. A total of 2 g/kg is administered over 2-4 days. This can be given monthly, if necessary, to maintain remission. Alternatively, prednisone at a dose of 2 mg/kg/day for 2 to 4 weeks and then a slow taper has been effective. If these modalities fail, splenectomy may be considered. Because asplenia predisposes children to infections with encapsulated bacteria, they should be immunized with pneumococcal, Haemophilus influenzae type B, and meningococcal vaccines prior to splenectomy. Platelet transfusion is reserved for the control of acute bleeding.
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