It is characterized by progressive lower extremity edema distal to the thigh, tight shiny skin, cyanosis (inadequate blood oxygenation), petechiae or purpura, and sudden severe pain of the affected limb in proportion to the level of venous blockage.

[4][5] Distal pulses are palpable early on but may diminish over time, and doppler signal can be usually heard throughout disease progression.

[10] Risk factors, present in around 50% of documented cases, include malignancy, hyper-coagulable states, cardiac disease, venous stasis, venous insufficiency, May-Thurner syndrome (right iliac artery compressing the left iliac vein that runs beneath it), surgery, trauma, pregnancy, inferior vena cava (IVC) filter, hormone therapy, oral contraceptives, prolonged immobilization, inflammatory bowel disease, heart failure, and central venous catheters.

[11][12][13] When a thrombus occludes an extremity vein, pressure backs up in the venous system leading plasma fluid to leak out into the interstitium of the affected limb.

This increases the pressure of that limb compartment, which can collapse the arteries and lead to acute ischemia, gangrene, hypovolemia, and hemodynamic instability.