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INTRODUCTION: Here we describe a patient with well-controlled HIV presenting with the classic pentad of TTP (fever, neurological manifestations, thrombocytopenia, renal dysfunction, microangiopathic hemolytic anemia) with undetectable ADAMS13 activity and elevated levels of inhibitor autoantibodies, in the absence of other risk factors for TTP. This case highlights the challenges of diagnosing idiopathic vs secondary TTP in the setting of HIV infection.

CASE DESCRIPTION: 43 y/o woman with PMHx HIV on raltegravir and truvada (last CD4 count 647 cells/µL, viral load undetectable 5 months prior), CAD who presented with transient left sided numbness x20 minutes, followed by headache and aphasia. MRI with multiple embolic appearing strokes in the bilateral cerebral hemispheres and cerebellar vermis. Patient thrombocytopenic to 15k/µL, Hb/Hct 8.4/24.0, creatinine elevated to 1.37 mg/dL.  LDH elevated at 721 U/L, with rare schistocytes noted on peripheral blood smear. Fibrinogen was normal, with undetectable haptoglobin and negative DAT. Hematology felt these laboratory values were consistent with a microangiopathic hemolytic anemia (MAHA). Overnight patient noted to have progressive aphasia, hyperreflexia and agitation, with low grade fevers to 100.9° F. ADAMS13 activity <4%, with level of the inhibitor autoantibody elevated to 68%. Patient emergently started on therapeutic plasma exchange x5 sessions with resultant normalization of neurological exam and laboratory values.

DISCUSSION: Thrombotic microangiopathies (TMAs) are well-recognized and documented complications of advanced HIV infection. HIV-associated secondary TTP is most commonly associated with CD4 counts <200 cells/μL, and is hypothesized to have a distinct pathophysiology compared to primary TTP, with only moderate decreases in ADAMS13 activity and absent/low levels of inhibitor autoantibodies. HIV-associated secondary TTP often responds to initiation of antiretroviral therapy. However, in patients with well-controlled HIV, a more classic idiopathic TTP must be considered and treated aggressively with plasma exchange, as in this case.