Phlebitis (inflammation of a vein) often occurs together with blood clot formation in the vein, known as thrombophlebitis. If phlebitis is mild, it may not produce any symptoms. When symptoms are present, pain, tenderness, bulging of the vein, warmth, and redness of the skin are the common symptoms. In some cases, fever may be present. Infections that cause phlebitis may lead to the drainage of pus from the involved site. Thrombi (clots) in thrombophlebitis can sometimes be felt in the form of hardened cords along the course of a vein. When thrombophlebitis occurs in the deep veins of the lower extremity, swelling of the leg as well as pain and tenderness can occur.