What is pulmonary embolism and pulmonary thromboembolism? Pulmonary embolism (PE) is a general term for a group of diseases or clinical syndromes whose pathogenesis is the obstruction of the pulmonary arterial system by various emboli, including pulmonary thromboembolism (PTE), fat embolism syndrome, air embolism, amniotic fluid embolism, foreign body embolism, bacterial embolism and tumor embolism. PTE is the most common type of pulmonary thromboembolism and is caused by obstruction of the pulmonary artery or its branches by thrombus from the venous system or the right heart, with pulmonary circulation and respiratory dysfunction as its main clinical and pathophysiological features. PTE is the most common type of PE and accounts for the majority of PE, which is commonly referred to as PTE. If the pulmonary artery is embolized, the lung tissue in the area of its innervation becomes necrotic due to obstruction or interruption of blood flow. What are the risk factors for pulmonary embolism? Risk factors that predispose to pulmonary embolism include primary and secondary risk factors. Primary risk factors are caused by genetic mutations, including factor V mutations, protein C deficiency, protein S deficiency, and antithrombin deficiency, and are often characterized by recurrent venous thromboembolism. If young patients under 40 years of age present with no obvious cause for venous thromboembolism, have recurrent venous thromboembolism, or show a family genetic predisposition, relevant genetic tests should be noted. Secondary risk factors refer to a variety of pathophysiological abnormalities acquired later in life that predispose to pulmonary embolism. These include fracture, trauma, surgery, malignancy, and oral contraceptive use. The above risk factors can be present alone or in concert and act synergistically. Age can be an independent risk factor, and the incidence of pulmonary embolism gradually increases with age. Clinical awareness of prevention and timely recognition of pulmonary embolism should be enhanced in cases where risk factors for pulmonary embolism are present, especially in cases where multiple risk factors are present at the same time. In patients with pulmonary embolism, attention should be paid to the possible hidden risk factors, such as malignancy, in some of them. Even if more complete technical means are actively applied to search for risk factors, there are still a considerable proportion of cases in which the risk factors cannot be identified clinically.