Deep vein thrombophlebitis affects the larger blood vessels, usually deep in the legs. Large blood clots can form, which may break off and travel to the lungs. This is a serious condition called ... Superficial thrombophlebitis is defined as the inflammation of a superficial vein, typically accompanied by the formation of a blood clot (thrombus) within that vein. This condition often occurs in the legs but can affect veins in other areas of the body. Phlebitis is inflammation of a vein near the surface of the skin, often in the legs. Learn about the symptoms, causes, treatments and when to get medical help for phlebitis. Phlebitis is inflammation of a vein, while thrombophlebitis is a blood clot causing inflammation. Learn about the types, causes, risk factors, diagnosis, treatment, and prevention of phlebitis and thrombophlebitis .