Protein S deficiency is a rare clotting problem that you can inherit from your parents. Many people with this deficiency don’t get a dangerous blood clot, but others can have a deep vein thrombosis or pulmonary embolism. Your provider may want you to take blood thinners to prevent too much clotting if you have this disorder.
Protein S deficiency is a rare disorder (usually inherited) that lets your blood clot too easily. Protein S helps keep other coagulation proteins from making too many blood clots. It’s one of many natural anticoagulants or substances that keep your clotting mechanism in check. When you have too little protein S, it’s harder for your body to control the coagulation pathway. This can result in excessive clotting.
Having this deficiency puts you at risk for a blood clot in your leg or arm veins that’s known as a deep vein thrombosis (DVT). If one of these blood clots gets to your lungs, it becomes a pulmonary embolism or PE that’s even more dangerous. Blood clots can also form in your brain or abdomen, but that’s not as common.
It’s important to note that many people with this disorder never develop blood clots.
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Mild protein S deficiency is a hereditary type of thrombophilia or clotting disorder, and is more common than the severe form of the disorder. Protein S deficiency can affect anyone who has the genetic mutation, regardless of gender.
When you have protein S deficiency, you’re more likely to have a DVT or PE, especially when these risk factors are present:
People with protein S deficiency may experience:
A mutation or change in your PROS1 gene causes a protein S deficiency. This is an inherited problem, which means you get it from one or both parents. You will have a mild protein S deficiency if you get it from one parent or severe protein S deficiency if you get protein S gene mutations from each parent. If you have a PROS1 mutation, you have a 50% chance of passing it on to each of your children.
The acquired form of protein S deficiency is more common and can be seen in the following situations or conditions:
Your provider may suspect you have a protein S deficiency if:
To diagnose you, your provider will want:
Your healthcare provider will want to treat you with a blood thinner or anticoagulant if you’ve had a venous thrombosis. If your provider finds you have protein S deficiency but haven’t had a blood clot, you are unlikely to require treatment except under certain circumstances.
Anticoagulants in common use include heparin, warfarin, rivaroxaban, apixaban and dabigatran. If your provider selects warfarin, they have to start heparin first to prevent a complication in which there is widespread clotting, including in the skin and soft tissues. However, this isn’t necessary with the other anticoagulants. Your provider will continue treatment for several months or the rest of your life depending on the circumstances in which your blood clot occurred.
If you have the mutation for protein S deficiency but haven’t had a blood clot, your provider will want to keep you from getting one. They may tell you not to take certain medicines like birth control pills that can promote blood clotting.
You may also need to take a blood thinner when:
If you’re taking warfarin, you’ll need to keep getting the INR blood test weekly or monthly so your provider can be sure you’re getting the right dose. The amount of warfarin you take today may be different from the amount you take in two months. The goal is to take the right amount of warfarin to prevent dangerous clots but also prevent a bleeding complication. Your provider will also monitor you if they’re giving you heparin in the hospital, but won’t need to monitor you as closely for other anticoagulants.
When your provider gives you heparin through an IV, it works in a few minutes. Warfarin can take up to a week to work, so your provider may not release you from the hospital until your INR is in the correct range.
If you were born with a protein S deficiency, you can’t prevent it. However, many people with this deficiency never have a blood clot. You may not be able to avoid the medical conditions that can cause acquired protein S deficiency, but you can avoid birth control pills and make sure you get enough vitamin K.
People with this disorder can have different experiences with it, so it’s difficult to predict your risk of blood clots, how bad the symptoms will get, how often you’ll get them or at what age they could start. Newborn babies who have the severe form of protein S deficiency can get blood clots in their small blood vessels (purpura fulminans), which can be fatal if it’s not treated.
Up to 40% of people who inherit a single protein S gene mutation (mild form of the disorder) won’t have a dangerous blood clot. Those who do get one usually have one before middle age and do well with treatment. Knowing your risk of dangerous clots and what to do if one happens can help you make a plan of action.
If you inherited a protein S deficiency, you’ll have it for life. If you acquired protein S deficiency, it should go away when the condition that caused it is gone.
If you take an anticoagulant, try to prevent bleeding. Use caution with knives and try a soft toothbrush and electric razor. Also, know the warning signs of a deep vein thrombosis and pulmonary embolism.
If you’re taking an anticoagulant, call your provider when you fall or have abnormal bleeding, such as a nosebleed or blood in your pee or poop. Also, call your provider if you think you’re having a deep vein thrombosis.
If you take an anticoagulant, call 911 if you‘re vomiting or coughing up blood, have a head injury or sudden severe headache, or can’t stop bleeding. You should also go to the ER if you think you are having symptoms of a pulmonary embolism (shortness of breath, chest pain, rapid heart rate and dizziness).
A note from Cleveland Clinic
If you know you have protein S deficiency, you can get peace of mind from knowing the symptoms of a deep vein thrombosis and a pulmonary embolism. You can empower yourself and your loved ones by knowing what to watch for and what to do if these symptoms develop. If your provider gives you a prescription for a blood thinner, be sure to take the exact amount they tell you to take. If you’re on warfarin, be sure to get your blood checked weekly or monthly to be sure you’re taking the correct dose.
Last reviewed by a Cleveland Clinic medical professional on 09/28/2021.
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