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:
- Significant swelling
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:
- Tenderness or pain, often in or around the vein with the blood clot
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.