Heparin-Induced Thrombocytopenia in a Patient With Postoperative Pulmonary Embolism: D-dimer Re-elevation and Progressive Pulmonary Artery Thrombosis.

Heparin-induced thrombocytopenia (HIT) is a rare but serious immune-mediated complication of heparin therapy, characterized by thrombocytopenia and paradoxical thrombosis. We report a case of HIT in an 83-year-old woman who developed postoperative pulmonary embolism (PE). Continuous unfractionated heparin was initiated, leading to initial improvement. However, seven days after PE and heparin initiation, thrombocytopenia and D-dimer re-elevation occurred without new symptoms. Her 4Ts score was 7, prompting a switch from heparin to argatroban. HIT antibodies were subsequently confirmed, and computed tomography (CT) revealed a new thrombus in the main pulmonary artery. Argatroban was later replaced with edoxaban after platelet recovery. Both thrombocytopenia and D-dimer levels gradually improved, and the patient was discharged 30 days after PE onset. Outpatient follow-up CT confirmed complete thrombus resolution. Clinicians should maintain a high index of suspicion for HIT in heparin-treated patients presenting with thrombocytopenia, with supportive laboratory findings such as unexpected D-dimer elevation, even in the absence of new or worsening symptoms. Early recognition and prompt management are essential to improve outcomes and prevent severe complications or death.