SERPINE1 and pulmonary embolism: Since the diagnosis of mixed hereditary and acquired thrombophilia was established, along with a history of pulmonary infarction in a relatively young patient, elevated PAI-1 levels combined with AC polymorphism are associated with an increased risk of pulmonary embolism due to their effects on the renin-angiotensin-aldosterone system, which regulates blood pressure and vascular homeostasis.