Thrombophilia is an inherited or acquired susceptibility to thrombosis due to an abnormality of blood coagulation. Factor II-related thrombophilia (also known as prothrombin-related thrombophilia) is the second most common form of thrombophilia after factor V Leiden. While many individuals with factor II-related thrombophilia do not develop blood clots, there is a 2-5 fold increased risk for thrombosis over that of the general population. Thrombotic risks associated with factor II-related thrombophilia can include deep-vein thrombosis, pulmonary embolism, myocardial infarction, and cerebral-vein thrombosis.

F2 is the only gene known to be associated with factor-II related thrombophilia, and encodes the protein prothrombin. Individuals with factor II-related thrombophilia are heterozygous or homozygous for a specific mutation, 20210G>A, in the F2 gene. Heterozygosity occurs in 1.7-3% of Caucasian population in the United States and Europe, and is less common in other ethnic groups. Molecular testing of additional genes associated with thrombotic risk, including factor V Leiden and MTHFR, are also available at the Genetics Center Molecular Diagnostic Laboratory.