Harvard Health Letter

By the way, doctor: What might have caused my sister and brother-in-law's pulmonary embolisms?

Q. Within a three-month period, both my sister and her husband (both in their 40s) were hospitalized with pulmonary embolisms. Any thoughts on the cause? Could it be something in the air?

A . A pulmonary embolism is a blood clot (or a piece of one) that forms somewhere in the body, usually the veins of the legs, gets loose, travels through the bloodstream, and lodges in an artery in the lungs. The consequences are extremely variable, ranging from no symptoms at all if a small clot blocks a small artery to sudden death if a large one blocks a larger artery. In between those two extremes, symptoms may include sudden breathlessness, pain in the chest when taking in a deep breath, and a new pain or swelling in the calf or thigh, caused by the clots in the legs where the pulmonary embolism originated.

It's important that blood have the ability to clot. Without clotting, we'd bleed to death whenever a blood vessel wall was breached. But there's no good purpose served by a clot forming inside a vein that's not bleeding.

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