Delayed hypersensitivity to heparin in a patient with cancer: fondaparinux may be safe but needs to be tested

Venous thromboembolism, which includes both deep vein thrombosis and pulmonary embolism, is the second leading cause of death in patients with cancer (1). Anticoagulant therapy, such as heparin, is used for prophylaxis and treatment for thrombosis in patients with cancer. Heparin may cause all types of allergic reactions, particularly cell-mediated type IV and antibody-mediated type II reactions (2). Risk factors for cell-mediated hypersensitivity to heparins include female sex, obesity, and long treatment duration.