Mayo Clinic defines DVT as deep-vein thrombosis. DVT happens when a blood clot forms within one of the deeper veins in the body, typically the legs. DVT is considered a life-threatening illness.
Mayo Clinic reports that the symptoms of DVT are pain, cramping or swelling in one or both legs. Sometimes, DVT occurs without any obvious symptoms. DVT is a serious condition because pieces of the blood clot can break off, travel to the lungs and cause a pulmonary embolism, which results in death if not treated immediately. DVT is typically treated with medications, but surgery is required in extreme cases.