Abstract
A young male patient diagnosed with Klinefelter syndrome was admitted to our hospital via the emergency room with chief complaints of acute chest pain and dyspnea. Pulmonary thromboembolism was diagnosed from his chest CT images. His symptoms improved after he underwent thrombolysis and anticoagulation treatment. Klinefelter syndrome has a tendency towards hypercoagulability due to hormonal imbalance and one or more inherited thromophilic factors. Thus, Klinefelter syndrome patients with a past medical history of venous thromboembolism require continuous oral anticoagulation therapy for a period of at least six months.