Which deep‑vein thromboses are hereditary (run in families)?

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Last updated: October 30, 2026 • View editorial policy

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Hereditary Deep Vein Thromboses

*The most common hereditary DVTs that run in families are caused by Factor V Leiden (FVL) and Prothrombin G20210A (Factor II c.97G>A) mutations, followed by less common deficiencies in antithrombin III, protein C, and protein S 1.

Primary Inherited Thrombophilias

Most Common Genetic Causes

Factor V Leiden (FVL) is the single most common inherited risk factor for thrombosis, accounting for the majority of familial DVT cases 1, 2. This mutation eliminates an activated Protein C cleavage site, causing Factor V to be inactivated more slowly and generating excess thrombin.

Prothrombin G20210A (also called Factor II c.*97G>A or PT 20210G>A) is the second most common inherited thrombophilia 1, 2. This variant increases circulating prothrombin levels, enhancing clot formation potential.

Less Common but Higher-Risk Deficiencies

The following protein deficiencies are rarer but carry substantial thrombotic risk 1, 3:

  • Antithrombin III deficiency - more quantifiable association with VTE
  • Protein C deficiency - inherited as autosomal dominant
  • Protein S deficiency - inherited as autosomal dominant
  • Plasminogen deficiency - less commonly identified

These deficiencies represent loss-of-function mutations in natural anticoagulant proteins 3.

Risk Stratification by Genotype

High-Risk Thrombophilias

Homozygous FVL or Factor II mutations, and compound heterozygotes (both FVL and Factor II) are classified as high-risk thrombophilias 1. These genotypes significantly influence treatment decisions:

  • FVL homozygotes: OR 17.84 for VTE occurrence in family members 2
  • Compound heterozygotes: OR 6.69 for VTE 2
  • FVL heterozygotes: OR 3.49 for VTE occurrence in family members 2

Moderate-Risk Thrombophilias

Heterozygous FVL presents weaker risk (OR 1.56 for recurrence) 2, though this is still clinically relevant for family counseling and risk modification.

Clinical Inheritance Patterns

All major inherited thrombophilias follow autosomal dominant inheritance patterns 4. This means:

  • 50% chance of transmission to offspring when one parent is affected
  • Both males and females are equally affected
  • First thrombotic episodes typically occur before age 40 in affected individuals 4
  • Known genetic factors are present in approximately 25% of screening populations without family history and up to 63% of familial cases 1

Important Clinical Caveats

Incomplete Penetrance

A critical pitfall: most people with inherited thrombophilia never develop DVT 5. The absolute lifetime risk of VTE is approximately 11% in the general population 1, and thrombophilia increases but does not guarantee thrombosis.

Multifactorial Nature

Genetic predisposition typically interacts with environmental triggers to provoke thrombosis 1. Common risk factors that add to inherited risk include 6:

  • Obesity
  • Smoking
  • ABO blood group (non-O types)
  • Specific polymorphisms (F11, FGG)
  • Acquired factors: surgery, immobilization, pregnancy, oral contraceptives, cancer

Approximately 50% of first-time VTE cases are apparently unprovoked despite this multifactorial nature 1.

Family Heterogeneity

Even within families carrying the same thrombophilia defect, clinical VTE patterns show wide heterogeneity 6. This reflects the contribution of additional common genetic and environmental factors beyond the primary inherited defect.

When to Consider Genetic Testing in Families

Based on the 2025 ACMG guidelines, testing is recommended for 1:

  • Individuals with VTE at unusual sites (cerebral, splanchnic)
  • VTE provoked by pregnancy/postpartum or oral contraceptives
  • Personal VTE history with positive family history in first- or second-degree relatives
  • Personal VTE history with first-degree relative having VTE at young age
  • Siblings of known FVL or Factor II homozygotes

Testing is suggested for 1:

  • Asymptomatic pregnant individuals with first-degree relative who is FVL homozygous or compound heterozygous
  • Asymptomatic individuals contemplating estrogen use with affected first-degree relative

Universal screening of asymptomatic family members is not recommended 1, 5. Testing should only occur when results will influence clinical management decisions or enable meaningful risk reduction through counseling about preventive measures.

Testing Asymptomatic Minors

Do not test asymptomatic minors, as VTE rarely occurs before young adulthood even in homozygous states 1.

References

3
Research

Inherited risk factors for venous thromboembolism.

Nature reviews. Cardiology, 2014

5
Research

Inherited thrombophilias: Genetics and testing considerations.

Journal of the American Association of Nurse Practitioners, 2026

6
Research

Common Risk Factors Add to Inherited Thrombophilia to Predict Venous Thromboembolism Risk in Families.

TH open : companion journal to thrombosis and haemostasis, 2019

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.