Prothrombin-related thrombophilia

What kind of tests can determine if an individual has, or is a carrier of, prothrombin thrombophilia?

No clinical signs or symptoms are specific for prothrombin thrombophilia. A confirmed diagnosis of this condition requires specific genetic testing via DNA analysis of the F2 gene, which provides instructions for making the protein prothrombin. The test identifies the presence of a common change (mutation) called 20210G>A. An individual can be a heterozygote (having one mutated copy of the F2 gene) or a homozygote (having two mutated copies).

Most heterozygotes have a mildly elevated plasma concentration of prothrombin (which can be measured in a blood test) that is approximately 30% higher than normal. However, these values can vary greatly, and the range of prothrombin concentrations in heterozygotes overlaps significantly with the normal range. Therefore, plasma concentration of prothrombin is not reliable for diagnosis of this condition.

Individuals interested in learning more about testing for prothrombin thrombophilia should speak with a genetics professional or other healthcare provider.

Last updated on 05-01-20

How is prothrombin thrombophilia inherited?

Prothrombin thrombophilia is inherited in an autosomal dominant manner. For this condition, this means that having one mutated copy of the disease- causing gene ( F2) in each cell may be sufficient to cause signs or symptoms of the condition. The mutation in the F2 gene that causes prothrombin thrombophilia is called 20210G>A (also called the 20210G>A allele). An individual can be heterozygous (having the mutation in only one copy of the F2 gene) or homozygous (having a mutation in both copies of the F2 gene). Heterozygosity results in an increased risk for thrombosis; homozygosity results in more severe thrombophilia and/or increased risk for thrombosis.

All individuals reported to date with prothrombin thrombophilia who are heterozygous for the 20210G>A allele have had an affected parent. Because of the relatively high prevalence of this allele in the general population, occasionally one parent is homozygous or both parents are heterozygous for this allele.

When an individual who is heterozygous for the 20210G>A allele has children, each child has a 50% (1 in 2) risk to inherit that allele and also be heterozygous. An individual who is homozygous will always pass one of the 20210G>A alleles to each of his/her children. If two heterozygotes have children together, each child has a 25% (1 in 4) risk to be homozygous (having 2 mutated copies), a 50% risk to be heterozygous like each parent, and a 25% risk to inherit 2 normal copies of the F2 gene.

Last updated on 05-01-20

Name: National Blood Clot Alliance 8321 Old Courthouse Road Suite 255
Vienna, VA, 22182, United States
Phone: +1-703-935-8845 Toll Free: 1-877-466-2568 (877-4NO-CLOT) Email: Url:
Name: Clot Connect UNC Hemophilia and Thrombosis Center 6340 Quadrangle Drive, Suite 50
Chapel Hill, NC, 27517, United States
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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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