This might help - Phlebitis means inflammation of a vein. Thrombophlebitis is the term used when a blood clot in the vein causes the inflammation. Thrombophlebitis usually occurs in leg veins, but it may occur in an arm. The thrombus (clot) in the vein causes pain and irritation and may block blood flow in the veins. Phlebitis can occur in both the surface (superficial) or deep veins. * Superficial phlebitis affects veins on the skin surface. The condition is rarely serious and, with proper care, usually resolves rapidly. Sometimes people with superficial phlebitis also get deep vein thrombophlebitis, so a medical evaluation is necessary. * Deep vein thrombophlebitis affects the larger blood vessels deep in the legs. Blood clots (thrombi) can form, which may break off and travel to the lungs. This is a potentially life-threatening condition called pulmonary embolism.