An inflammation of a vein. Individuals with phlebitis typically experience tenderness, redness, and hardness along the course of the vein. The cause of the inflammation may be related to injury of the vein or infection. The presence of varicose veins and the long-term use of indwelling intravenous catheters or irritating intravenous solutions place individuals at risk of developing phlebitis. In addition, those with certain diseases, including systemic lupus erythematosus, vasculitis, or malignancy, are at increased risk.