ADAMTS13 activity levels in patients with human immunodeficiency virus-associated thrombotic microangiopathy and profound CD4 deficiency.

BACKGROUND: Thrombotic microangiopathy (TMA) encompasses a number of disorders with hemolytic anemia and thrombocytopenia, including thrombotic thrombocytopenic purpura (TTP). A deficiency in ADAMTS13 enzyme levels, along with an inhibitory antibody, is found in most patients with idiopathic TTP. Patients with human immunodeficiency virus (HIV) infection can have a TTP-like illness; however, it appears to have a different etiology.
METHODS: A retrospective review of patients who had an ADAMTS13 activity level performed from 2005 through 2007 was completed. Patients with a diagnosis of HIV infection with TMA were investigated.
RESULTS: Two patients were identified. Case 1: a 47-year-old man with HIV infection and a CD4 count <10/microL presented with altered mental status, pneumonia, acute renal failure, thrombocytopenia, and anemia. The ADAMTS13 level was 71%. He was treated with plasma infusion. Two days after admission, he expired because of respiratory distress syndrome and metabolic lactic acidosis. Case 2: a 39-year-old man with HIV infection and a CD4 count of 9/microL presented with chest pain, acute renal failure, thrombocytopenia, and anemia. The ADAMTS13 level was 65%. He received multiple units of fresh frozen plasma without significant improvement in his platelet count. Six days after admission, the patient began highly active antiretroviral therapy, which resulted in a rapid increase in his platelet count.
CONCLUSIONS: HIV-associated TMA is postulated to have a different pathophysiology than idiopathic TTP. This study supports that assumption because both patients exhibited many of the classic findings of TTP but did not have a deficiency of ADAMTS13. (c) 2009 Wiley-Liss, Inc.