A CASE OF SPONTANEOUS HEPARIN-INDUCED THROMBOCYTOPENIA AND THROMBOSIS (HITT)

Abstract

SESSION TITLE: Critical Care 2 SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/09/2018 01:15 PM - 02:15 PM INTRODUCTION: Spontaneous heparin-induced thrombocytopenia and thrombosis (HITT) is established with positive serum platelet factor 4 (PF4) antibody, thrombosis, and without prior heparin exposure. Only a handful of spontaneous HITT cases have been reported. Due to history of no exposure to heparin products, diagnosis is often challenging and treatment delayed leading to increased patient morbidity and mortality. Here we present a case of spontaneous HIT and thrombosis after a left total knee arthroplasty (TKA). CASE PRESENTATION: A 71 year old male presented on postoperative day (POD) 7 from left TKA with acute onset abdominal pain, bright red blood per rectum, and coffee ground emesis. Prior to his TKA, he was noted to have a platelet count of 185 x 103/uL. Post-operatively he was discharged on Clindamycin 600mg and Aspirin 325mg twice daily for deep venous thrombosis (DVT) prophylaxis. On admission, he was found to have a platelet count of 47 x 103/uL and further work-up revealed splenic vein and bilateral lower extremity deep venous thrombosis. Due to acute bleeding patient was not started on anticoagulation and an inferior vena cava filter was placed. On hospital day 3, patient became acutely short of breath and computed tomography angiogram of the chest revealed bilateral pulmonary artery emboli. Serum PF4 [define PF4 here] antibody resulted strongly positive at 3.004 optical density (OD) (Range: 0.0 – 0.4 OD) indicating HITT associated thrombosis. Once the serum PF4 antibody titer was resulted positive, patient was started on Argatroban drip with eventual increase in platelet count past 150 x 103/uL. DISCUSSION: HIT is a complication of exposure to heparin that could be life threatening. It is caused by autoantibodies that recognize and bind to highly antigenic multi-molecular complexes formed of heparin binding to endogenous protein PF4 and causing platelet activation.1 Multiple theories have been proposed but the exact mechanism behind spontaneous HIT remains unclear. In vitro studies have shown that heparin antibodies are not specific to heparin and can also recognize PF4 bound to other polyanions and have shown to be elicited by reaction with lipopolysaccharides from gram negative bacteria.2 This may explain why cases of spontaneous HIT are seen in patient following total knee or hip arthroplasty where significant limb ischemia and tissue injury occur. CONCLUSIONS: Although exceedingly rare, spontaneous HITT is important to be recognized early to reduce patient morbidity and mortality. Patients without prior exposure to heparin who have undergone orthopedic procedures and present with worsening platelet count or new arterial/venous thrombosis should be considered to have spontaneous HITT and treated accordingly. Reference #1: Rauova L, Zhai L, Kowalska MA, et al. Role of platelet surface PF4 antigenic complexes in heparin-induced thrombocytopenia pathogenesis: diagnostic and therapeutic implications. Blood 2006; 107:2346. Reference #2: G. Pongas, S. K. Dasgupta, and P. Thiagarajan, “Antiplatelet factor 4/heparin antibodies in patients with gram negative bacteremia,” Thrombosis Research, vol. 132, no. 2, pp. 217–220, 2013. Reference #3: Warkentin T.E., Cook R.J., Marder V.J., Greinacher A. Anti-PF4/heparin antibody formation postorthopedic surgery thromboprophylaxis: the role of nondrug risk factors and evidence for a stoichiometry-based model of immunization. J Thromb Haemost. 2010; 8:504. DISCLOSURES: No relevant relationships by Bryan Anderson, source=Web Response No relevant relationships by Chinthaka Bulathsinghala, source=Web Response No relevant relationships by Palla De Silva, source=Web Response No relevant relationships by Ahmed Hassan, source=Web Response No relevant relationships by aftab mahmood, source=Web Response No relevant relationships by Chirag Patel, source=Web Response Speaker/Speaker's Bureau relationship with Sunovian Please note: $5001 - $20000 Added 11/20/2017 by Salim Surani, source=Web Response, value=Honoraria Advisory Committee Member relationship with Astra Zeneca Please note: $5001 - $20000 Added 11/20/2017 by Salim Surani, source=Web Response, value=Consulting fee No relevant relationships by Deanna Yamamura, source=Web Response