Factor V Leiden

Factor V Leiden (FAK-tur five LIDE-n)is a mutation of one of the clotting factors in the blood called factor V. This mutation can increase your chance of developing abnormal blood clots (thrombophilia), usually in your veins.

Most people with factor V Leiden never develop abnormal clots. However, some people with factor V Leiden develop clots that lead to long-term health problems or become life-threatening.

Both men and women can have factor V Leiden, but women may have an increased tendency to develop blood clots during pregnancy or when taking the hormone estrogen.

If you have factor V Leiden and have developed blood clots, medications can lessen your risk of developing additional blood clots and help you avoid potentially serious complications.

Symptoms Causes Risk factors Complications

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.

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