What is Protein C Deficiency?

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  • Written By: Niki Foster
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  • Last Modified Date: 12 September 2019
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Protein C deficiency is a genetic trait that predisposes one to thrombotic disease, in which the blood clots too much, causing blood vessel blockages, or embolism. Protein C deficiency is associated with thrombosis in the veins, but not the arteries. The condition is very rare, affecting only 0.2 to 0.5% of the population.

Protein C is an anticoagulant, meaning that it prevents blood from clotting, or coagulating. Of course, clotting is a very important function of the blood, responsible for the healing of wounds. However, excessive clotting can cause problems of its own, including stroke and heart attack. Therefore, the body is naturally equipped with anticoagulant regulators, one of the most important of which is protein C.

There are two types of protein C deficiency. In Type I, the patient does not produce enough of the protein, while in Type II, the protein does not function correctly, interacting abnormally with other molecules. In most people with protein C deficiency, only one of the two genes responsible for protein C is dysfunctional, so there is still some functioning protein C in the blood.


Some people are born with two defective copies of the gene responsible for protein C, resulting in a complete deficiency of the protein. While this condition is extremely rare, it can lead to the development of purpura fulminans, also called purpura gangrenosa, in infants. This life threatening condition is characterized by the formation of numerous small clots within blood vessels, excessive bleeding, necrosis or tissue death, fever, and low blood pressure. Homozygous protein C deficiency, in which both the relevant genes are defective, must be treated very early with supplemental concentrates of protein C.

Heterozygous protein C deficiency, in which only one gene is defective, is usually treated by administering anticoagulant medication, such as aspirin, heparin, or warfarin. Such medications are typically taken regularly to prevent clotting, rather then in response to a thrombotic episode. Anticoagulant medication is usually prescribed long-term for people with protein C deficiency, often for life.

In a related, but extremely rare condition, the drug warfarin can induce protein C deficiency in patients who were not born with the condition. Though it is an anticoagulant, warfarin also inhibits protein C. In warfarin necrosis, excessive clotting prevents blood flow to the skin, resulting in lesions that eventually hemorrhage. Other anticoagulants do not have this issue, and they are sometimes given along with warfarin in the beginning of warfarin treatment to prevent warfarin necrosis.


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Post 3

@burcidi-- Did you take any other anticoagulants during your second pregnancy other than aspirin?

I have a protein C & S deficiency too and although I didn't have preeclampsia during my pregnancy, it was still a difficult time. Before I got pregnant, I was taking an anticoagulant called warfarin in tablet form. When my husband and I decided to try for a baby, my doctor had me switch to another kind of anticoagulant- Heprin- which has to be injected.

It was not fun injecting myself everyday but I had to learn. Unfortunately warfarin isn't allowed during pregnancy, but I switched back after the baby.

Post 2

@burcidi-- Actually, protein C and protein S deficiency can be acquired as well as genetic. Protein S is another natural anticoagulant. And many people who have a protein C deficiency have a protein S deficiency as well.

Back to the topic, this deficiency can be acquired, but as far as I know it happens due to serious illness and I don't think that preeclampsia could cause it.

Plus, genetic testing can tell you if it is a hereditary condition or if it was acquired. If you haven't suffered from severe illness, it must be genetic. And you probably just did not get diagnosed until you had detailed lab work done during your pregnancy.

When it's a genetic condition, one of the parents generally have it as well and genetic testing will show that.

Post 1
I had preeclampsia in both of my pregnancies. Preeclampsia is where pregnancy causes hypertension and it's a dangerous condition. I lost my first baby due to very high pressure that forced me to give birth too early. It was at this time that I found out I have a protein C deficiency.

My doctor put me on aspirin right away and I continued to take aspirin throughout my second pregnancy. I still had high blood pressure, but I was much more careful the second time around. I carried full term and had a healthy baby.

At first I thought that the preeclampsia was the cause of the deficiency but I haven't heard of any other women who have experienced the same. And since protein C deficiency disease is genetic, it must be a coincidence that I found out about it at the same time.

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