Don't Miss the Hit: Thrombocytopenia and Thrombosis in a High-Risk Cancer Patient

Document Type

Conference Proceeding

Publication Date

5-2026

Publication Title

American Journal of Respiratory and Critical Care Medicine

Abstract

Introduction: Heparin-induced thrombocytopenia (HIT) is an immune-mediated prothrombotic disorder driven by anti-PF4-heparin antibodies that activate platelets and generate thrombosis despite falling platelet counts. Diagnosing HIT in patients with suspected or active malignancy is challenging, as cancer-associated thrombosis, consumptive coagulopathy, and procedural platelet shifts may obscure the diagnosis. Although venous thrombosis predominates, arterial thromboses represent 20-30% of HIT-related events and are associated with higher rates of limb loss and death. HIT may occur even after subcutaneous unfractionated heparin (UFH) prophylaxis, with reported incidence ~0.5-1% in medical inpatients and ~2-3% in postoperative patients, significantly higher than with LMWH (< 0.3%). We present a case of confirmed HIT with extensive arterial and venous thromboses in a patient undergoing evaluation for suspected ovarian malignancy. Case Presentation: A 67-year-old woman undergoing work-up for presumed ovarian cancer presented with acute dyspnea and progressive leg swelling shortly after outpatient paracentesis. CT angiography revealed bilateral pulmonary emboli with right heart strain and simultaneous arterial and venous thromboses, including occlusion of the abdominal aorta, iliac arteries, and femoral artery—an unusually extensive pattern suggestive of a systemic prothrombotic trigger. Platelets declined from >400 × 109 /L to 72 × 109 /L. She developed worsening anemia requiring transfusion and a large flank ecchymosis. Given her hemodynamic instability, the patient required admission to the medical intensive care unit (MICU) for close and frequent hemodynamic monitoring, ongoing transfusion needs, and management of evolving thromboses. She had been discharged three days earlier from a hospitalization in which she received subcutaneous UFH for VTE prophylaxis. The >50% platelet fall, timing consistent with day 5-10 after exposure, and new multi-bed thromboses yielded a 4Ts score of 7 (high probability). Argatroban was initiated empirically. PF4 ELISA was positive (OD 0.547), and serotonin release assay confirmed HIT with 91% serotonin release at low-dose heparin and inhibition at high dose. Discussion: This case illustrates a fulminant HIT presentation with concurrent arterial and venous thromboses, a pattern associated with poor outcomes. Despite malignancy-related confounders, structured application of the 4Ts score enabled timely discontinuation of heparin and initiation of a direct thrombin inhibitor. Clinicians should maintain vigilance for HIT even after prophylactic UFH exposure. Conclusion: Abrupt thrombocytopenia with widespread thrombosis following recent heparin exposure requires prompt evaluation for HIT. Early recognition, confirmatory testing, and rapid transition to non-heparin anticoagulation are critical to preventing life-threatening complications.

Volume

212

Issue

S1

First Page

S2472

Comments

American Thoracic Society International Conference, May 15-20, 2026, Orlando, FL

Last Page

S2472

DOI

10.1093/ajrccm/aamag162.3283

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