Factor V Leiden

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Factor V Leiden

Hematological system

Coagulation disorders


Vitamin K deficiency

Leukemoid reaction

Leukemoid reaction


Factor V Leiden


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USMLE® Step 1 questions

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High Yield Notes

6 pages


Factor V Leiden

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USMLE® Step 1 style questions USMLE

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A 52-year-old woman, para 4 gravida 2 aborta 2, comes to the clinic for a follow-up appointment after a hospitalization. Two weeks ago, she had an incident of acute, severe abdominal pain and bloody stools. She was diagnosed with portal vein thrombosis. She denies similar episodes in the past. Medical history is notable for Legg-Calvé-Perthes disease as a child. She does not smoke, drink excessive alcohol, or use illicit drugs. She had 2 spontaneous abortions in the first trimester, following 2 successful pregnancies. Family history is remarkable for DVT in her maternal uncle and colon cancer in her father. The physician suspects an inherited condition. Which of the following will prompt further evaluation in this patient?  

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Factor V Leiden p. 418, 435

venous sinus thrombosis and p. 519


Factor V Leiden is a disorder where blood clots form more easily due to a mutation in a clotting protein called factor V. Factor V Leiden is the most common hypercoagulable disorder in people of caucasian descent, and was named after the town Leiden in Holland, where the disease was first described.

Now, Factor V Leiden is a hemostasis disorder.

Hemostasis is the process where blood flow is stopped after there’s damage to a blood vessel, and it has two steps.

Primary hemostasis involves the formation of a platelet plug at the site of injury, and secondary hemostasis involves the coagulation cascade, where several clotting factors come into play to form a fibrin mesh over the platelet plug to reinforce it - forming a blood clot.

Hemostasis can be both stimulated, and inhibited by several factors.

One way to stimulate hemostasis is with thrombin, or factor II, which increases platelet activation, and cleaves several factors involved in secondary hemostasis to their active form.

So one way to inhibit hemostasis is actually to inhibit thrombin.

This happens with the help of anticoagulant proteins like protein C. Protein C is a vitamin K dependent circulating plasma protein produced in the liver along with a cofactor called protein S.

Both protein C and S interact with a protein called thrombomodulin, which is on the surface of intact endothelial cells that line our blood vessels.

So, let’s say you cut your finger and now a blood clot has formed.

When there’s a lot of thrombin around a damaged blood vessel, excess thrombin binds to thrombomodulin and it can no longer participate in the coagulation cascade.


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  2. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  3. "Harrison's Principles of Internal Medicine" McGraw-Hill (2004)
  4. "Factor V Leiden" Radiol Technol (2019)
  5. "Factor V Leiden thrombophilia" Genet Med (2011)
  6. "Factor V Leiden" The Journal of Perinatal & Neonatal Nursing (2003)
  7. "Diagnosis and management of<i>factor V Leiden</i>" Expert Review of Hematology (2016)

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