What are some of the causes of blood clots in a persons lungs?

Answer 1

Unless there is some kind of really rare vascular abnormality in the lung, the clots don't form there but move there from other places., most commonly the legs.

In addition to prolonged immobilization of the legs, like taking a long flight, clots can form as a result of taking medication, most commonly birth control pills, especially if one smokes as well. Smoking itself increases the risk of blood clots, and some people are born with coagulation disorders that only can be identified after they are investigated following their first episode of clotting. One can get clots in association with some autoimmune diseases, such as Lupus, and as well, very rarely, abnormal clotting can be a manifestation of underlying malignant disease.

Answer 2

One of the causes of blood clots in a person's lungs is known as the pulmonary embolism which is the blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream.