Thrombocytopenia and immune thrombocytopenic purpura

Thrombocytopenia is commonly observed in people with HIV infection with immune thrombocytopenic purpura (ITP) the most common cause of severe thrombocytopenia (platelet count < 30 x 10^9/L). It may occur in 30% or more of patients with AIDS13 and can occur at any time during HIV infection. In the antiretroviral era, risk factors include HIV viral load > 400 copies/mL, hepatitis C virus co-infection and cirrhosis.¹⁴ It may be seen before other clinical manifestations of HIV infection. Therefore, HIV antibody testing is recommended in the assessment of new cases of thrombocytopenia. Platelet depletion in HIV-associated ITP has several causes. Immune complexes of antibodies to HIV glycoprotein (gp) 120 may bind the platelet membrane GPIIIa complex15  and it appears that megakaryocytes may be directly infected  by HIV.1   Platelet  survival is decreased, especially in patients with only mild-to-moderate depletion of CD4+ T cells,  as is platelet production.1  Other common causes of thrombocytopenia in HIV patients are drugs, such  as ganciclovir, cotrimoxazole and rifabutin, infections  such as  Mycobacterium   avium complex  (MAC), lymphoma and hypersplenism (most commonly due to liver disease. Rarer causes that appear directly related to HIV infection are thrombotic microangiopathies, thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome.  Bleeding is uncommon n  ITP  unless  the  platelet  count  is < 30 x 109/L. However, patients with co-existing haemophilia or other coagulopathies should be treated if platelet counts fall below 50 x 109/L.16 The treatment of choice for ITP is cART. Corticosteroids are effective but long-term use is not desirable due to immunosuppression.  Other drugs such as dapsone and danazol can be effective. Intravenous immunoglobulin is very effective in increasing platelet counts in the short term but is expensive. Splenectomy may be successful for refractory cases and does not increase risk of progression to AIDS.16  The thrombopoietin receptor agonists, romiplostim and eltrombopag may also be effective and considered for patients with refractory ITP ¹⁷ who are not fit for splenectomy.  For other causes of thrombocytopenia, treatment of the underlying cause is usually effective. Support with platelet transfusions should only be considered for patients at immediate risk of bleeding as the effect of transfusion is short lived and platelet allo-antibodies rapidly develop, limiting the effectiveness of future transfusions.