Definition
Phlebitis is the term for the swelling of a vein, most often in one’s leg. Thrombophlebitis is the term for inflammation of a vein caused by a blood clot. The term is often shortened to phlebitis. The condition is easily treatable, though it sometimes leads to more serious health concerns.
Thrombophlebitis

There are two kinds of phlebitis: superficial phlebitis (affecting veins near the skin's surface) and deep venous thrombosis (DVT).
When the clot is embedded into a deep vein, thrombophlebitis can become much more serious. The condition, appropriately named deep vein thrombosis , can cause blood clots in the lungs ( pulmonary embolism ), heart attack , and stroke .