Clinical Challenges in Profound Thrombocytopenia Associated With Type 2 Heparin-Induced Thrombocytopenia (HIT2)

This case describes an unusually severe presentation of immune-mediated heparin-induced thrombocytopenia type 2 (HIT2), marked by an abrupt and profound decline in platelet count to levels below 2000/µL. Although HIT typically presents with moderate thrombocytopenia and thrombotic complications, such an extreme nadir in the absence of disseminated intravascular coagulation (DIC) or other hematologic disorders is highly atypical. The patient's course reinforces the need to consider HIT even when thrombocytopenia appears disproportionately severe and highlights that appropriate anticoagulation can be initiated safely despite concurrent bleeding, provided the diagnosis is promptly recognized. A 76-year-old man with chronic kidney disease, diabetes, and cardiovascular disease was admitted with acute respiratory failure, community-acquired pneumonia, and a non-ST-elevation myocardial infarction complicated by complete heart block. He received multiple heparin products, including IV continuous heparin, prophylactic dosing, and heparin flushes for catheter maintenance, as well as piperacillin-tazobactam during his hospitalization. Within 12 hours, he developed mucosal bleeding, widespread purpura, and a sudden drop in platelet count from 93000/µL to below 2000/µL. Laboratory testing confirmed the diagnosis of HIT2, and alternative diagnoses such as DIC and thrombotic thrombocytopenic purpura were clinically excluded. Treatment included immediate cessation of heparin, initiation of argatroban, high-dose intravenous immunoglobulin, and corticosteroids. The patient's platelet count improved after the withdrawal of both heparin and piperacillin-tazobactam; however, re-exposure to the antibiotic later provoked another platelet decline, suggesting a secondary drug-induced immune mechanism. This case illustrates the diagnostic and therapeutic challenges posed by severe thrombocytopenia in HIT, especially when overlapping medication effects and bleeding risks complicate management decisions. It emphasizes the importance of timely recognition and the careful balancing of anticoagulation in patients at risk for both thrombosis and hemorrhage.