(Undated) -- The CDC says up to 600-thousand people are affected by deep vein thrombosis. Doctor Natalie Evans says one symptom is bulging veins that weren't there before. D-V-T is a blood clot that develops deep in the body, usually in the thigh, leg or pelvis. About a third of people diagnosed with D-V-T suffer from post thrombotic syndrome due to the damage done by the blood clot. P-T-S causes a burning sensation, cramping and heaviness in the legs.