Protein C Deficiency
A clotting disorder from too little of the natural blood thinner protein C
Quick Facts
- Type: Inherited clotting tendency (thrombophilia)
- Affected protein: Protein C, a natural anticoagulant
- Main risk: Blood clots, especially in leg veins
- Often inherited: Runs in families
Overview
Protein C deficiency is a blood clotting disorder in which the body does not have enough working protein C. Protein C is a natural anticoagulant, meaning it helps keep blood from clotting too much by switching off parts of the clotting process. When levels are low, blood is more likely to form clots inappropriately, a tendency known as thrombophilia.
Most cases are inherited and run in families, caused by a change in the gene that makes protein C. People who inherit one altered copy have a mild to moderate increase in clotting risk and may go their whole lives without a problem, while those who inherit two altered copies can have a much more severe form that appears in infancy. Protein C levels can also drop temporarily because of other illnesses or certain medicines. Understanding the deficiency helps guide prevention and treatment of clots.
Symptoms
Protein C deficiency itself causes no symptoms; problems arise only if a blood clot forms. The most common clots are in the deep veins of the legs (deep vein thrombosis) and the lungs (pulmonary embolism). Warning signs include:
- Swelling, pain, redness, or warmth in one leg (possible deep vein thrombosis)
- Sudden shortness of breath, chest pain, or coughing up blood (possible pulmonary embolism, a medical emergency)
- Clots in less usual locations in some cases
The rare severe form in newborns can cause widespread clotting in the skin and other tissues soon after birth and is a medical emergency.
Causes
Protein C deficiency can be inherited or acquired.
- Inherited: A change in the gene for protein C, passed down in families. Inheriting one altered copy causes a mild to moderate deficiency; inheriting two can cause a severe form in infancy.
- Acquired: Protein C levels can fall temporarily with severe infection, liver disease, vitamin K deficiency, certain medications such as warfarin when first started, or other serious illness.
Whatever the cause, the result is reduced control over clotting and a higher chance of abnormal clots.
Risk Factors
In someone with protein C deficiency, the chance of a clot is higher when other clotting risks are also present:
- Surgery, injury, or prolonged immobility (such as long travel or hospital stays)
- Pregnancy and the period after childbirth
- Estrogen-containing birth control or hormone therapy
- Other inherited clotting disorders
- Older age, obesity, and smoking
Diagnosis
Protein C deficiency is diagnosed with blood tests, often after an unexplained or early clot or because of a family history.
- Protein C activity test: Measures how well protein C is working in the blood.
- Repeat and confirmatory testing: Levels can be affected by acute clots, illness, and blood thinners, so testing is usually repeated at an appropriate time and may include genetic testing.
- Family testing: Relatives may be tested if an inherited deficiency is found.
Testing is best interpreted by a specialist, since timing and medications strongly affect results.
Treatment
Treatment depends on whether a clot has occurred and on a person's overall risk.
- No clot: Many people with mild deficiency and no clots take no regular medication but use preventive blood thinners temporarily during high-risk times such as surgery, hospitalization, or after childbirth.
- Active clot: Blood-thinning (anticoagulant) medication treats a clot and prevents it from growing or spreading.
- Long-term anticoagulation: Considered for people with recurrent or serious clots, guided by a specialist.
- Severe newborn form: Requires urgent specialist treatment, which may include protein C replacement and anticoagulation.
Decisions are individualized, balancing the risk of clots against the risk of bleeding from blood thinners.
Prevention
- Tell your healthcare providers about your deficiency before surgery, hospital stays, or pregnancy
- Move regularly and stay hydrated during long travel
- Discuss safer contraception options if you use estrogen-containing methods
- Avoid smoking and manage weight
- Learn the warning signs of a clot and seek care quickly if they occur
When to See a Doctor
See a healthcare provider if you have a personal or family history of blood clots, especially at a young age or without an obvious cause, so testing and prevention can be considered. Seek emergency care immediately for signs of a clot, including swelling, pain, or redness in one leg, or sudden shortness of breath, chest pain, or coughing up blood, which may indicate a clot in the lungs and is life-threatening.
Frequently Asked Questions
What is protein C deficiency?
It is a blood clotting disorder in which the body has too little working protein C, a natural blood thinner. With less protein C, blood is more likely to form abnormal clots, especially in the deep veins of the legs and the lungs.
Is protein C deficiency inherited?
Most cases are inherited and run in families. Inheriting one altered gene copy causes a mild to moderate deficiency, while two altered copies can cause a severe form in newborns. Levels can also drop temporarily from illness or certain medicines.
Does everyone with protein C deficiency get blood clots?
No. Many people, especially those with a mild deficiency, never have a clot. The risk rises during high-risk situations such as surgery, immobility, pregnancy, or estrogen use, which is when extra precautions and sometimes preventive blood thinners are used.
How is protein C deficiency treated?
If a clot occurs, blood-thinning medication treats it and prevents spread. Many people without clots take no daily medicine but use preventive blood thinners during high-risk times. Long-term anticoagulation is considered for recurrent or serious clots, guided by a specialist.
References
- MedlinePlus, U.S. National Library of Medicine. Protein C deficiency.
- National Heart, Lung, and Blood Institute (NHLBI). Venous Thromboembolism.
- National Blood Clot Alliance. Inherited clotting disorders.