Most people who have factor V Leiden never develop signs or symptoms. However, the first indication that you have the disorder may be the development of a blood clot (thrombosis).

Some clots do no damage and disappear on their own. Others can be life-threatening. Symptoms of a blood clot depend on where it forms and whether and where it travels.

A clot developing in a deep vein

This is known as deep vein thrombosis (DVT). A DVT may not cause any symptoms. If signs and symptoms do occur, they commonly affect your legs, including your ankles and feet, and may include:

  • Pain
  • Significant swelling
  • Redness
  • Warmth

A clot that forms closer to the surface of your skin

This is referred to as superficial venous thrombosis, phlebitis or thrombophlebitis. Signs and symptoms usually include:

  • Warmth
  • Tenderness or pain, often in or around the vein with the blood clot
  • Redness

A clot that travels to your lungs

Known as a pulmonary embolism, this occurs when a deep vein clot breaks free and travels through the right side of your heart to your lung, where it blocks blood flow. Symptoms may include:

  • Sudden shortness of breath
  • Chest pain when breathing in
  • A cough that produces bloody or blood-streaked sputum
  • Rapid heartbeat (tachycardia)

When to see a doctor

Seek medical attention immediately if you:

  • Have signs or symptoms of a pulmonary embolism, such as chest pain or discomfort.
  • Have signs or symptoms of DVT, such as leg pain and swelling.

See a doctor if you:

  • Have a family history of blood clots or if family members have factor V Leiden. Ask your doctor about the risks and benefits of genetic testing for the disorder.
  • Have had one or more blood-clotting incidents without an apparent cause, especially if you're under 50.
Sep. 06, 2012