The most common genetic disorder causing blood to clot when it shouldn’t is called Factor V Leiden thrombophilia. Here is what the National Institutes of Health’s Genetics Home Reference Web site says about the disorder:

“Between 3 and 8 percent of people with European ancestry carry one copy of the Factor V Leiden mutation in each cell, and about 1 in 5,000 people have two copies of the mutation. The mutation is less common in other populations. . . .

“People with Factor V Leiden thrombophilia have a higher than average risk of developing a type of a deep venous thrombosis (DVT). DVTs occur most often in the legs, although they can also occur in other parts of the body, including the brain, eyes, liver, and kidneys. Factor V Leiden thrombophilia also increases the risk that clots will break away from their original site and travel through the bloodstream. These clots can lodge in the lungs, where they are known as pulmonary emboli. Although Factor V Leiden thrombophilia increases the risk of blood clots, only about 10 percent of individuals with the Factor V Leiden mutation ever develop abnormal clots.”

Among the symptoms that may suggest such a mutation are: having a first DVT (or blood clot that passes into your lungs) before age 50 or having recurring DVTs; for women, having a DVT during or right after pregnancy; and having a thrombosis is an uncommon spot, such as the liver or brain. According to the Mayo clinic, Factor V Leiden mutation can be diagnosed with a blood test.