http://www.cdc.gov/Features/Thrombosis/
Centers for Disease Control and Prevention, U.S. Department of Health and Human Services
Deep vein thrombosis occurs when a blood clot forms in a large vein. Part of a clot may break off and travel to the lungs, causing a pulmonary embolism and, possibly, death. Everybody should know the risk factors, symptoms, and steps they can take to protect themselves.