Thrombocytosis

Thrombocytosis is a condition where your body has too many platelets in the blood. While many people have no symptoms and may not need treatment, understanding this condition is important because it can sometimes increase the risk of blood clots or, less commonly, bleeding problems.

Table of contents

• What is thrombocytosis?
• Types of thrombocytosis
• Signs and symptoms
• What causes thrombocytosis?
• How is thrombocytosis diagnosed?
• Treatment approaches
• Possible complications
• Living with thrombocytosis

What is thrombocytosis?

Platelets are tiny parts of your blood that help form blood clots. When you cut yourself, platelets stick together to create a plug that stops the bleeding. Thrombocytosis is a disorder in which your body produces too many platelets^[1].

The normal platelet count in an adult ranges from 150,000 to 450,000 platelets per microliter of blood. When your platelet count rises above 450,000 per microliter, you may be diagnosed with thrombocytosis^[5]. A high platelet level may be detected during a routine blood test known as a complete blood count^[1].

Many people with high platelet levels don’t have signs or symptoms. In fact, this condition is often discovered only after routine blood tests^[9]. However, when too many platelets build up in your blood, they can make your blood too sticky. In serious cases, they can cause harmful blood clots that may lead to a heart attack or stroke^[7].

Types of thrombocytosis

There are two main types of thrombocytosis, and it’s important to determine which type you have to choose the best treatment options^[1].

Reactive thrombocytosis, also called secondary thrombocytosis, is the more common type. It occurs when a high platelet count is a response to something else, such as an infection or surgery. This type is usually temporary^[7]. The high platelet count happens because your body is reacting to an underlying condition or trigger^[5].

Essential thrombocythemia, also known as primary thrombocythemia or essential thrombocytosis, is less common. When the high platelet count has no apparent underlying condition as a cause, the disorder is called essential thrombocythemia. This is a blood and bone marrow disease^[1]. Essential thrombocythemia is an acquired genetic condition, meaning it happens when certain genes mutate or change^[3].

Essential thrombocythemia is a chronic myeloproliferative neoplasm, which is a type of blood disorder that happens when your body produces too many blood cells^[3]. Approximately 55% of patients with essential thrombocythemia have the Janus kinase 2 (JAK2) mutation. Other people with this condition may have mutations in the CALR (calreticulin) gene or the MPL gene^[2][4].

Signs and symptoms

Most people with high platelet counts don’t have symptoms. If you have reactive thrombocytosis, you may have symptoms related to the condition causing it^[7].

When symptoms do occur, they’re often related to blood clots. Thrombocytosis that leads to clots inside your body can cause noticeable changes. This is more common with essential thrombocythemia. Examples of symptoms include^[1][7]:

• Headache
• Confusion or changes in speech
• Chest pain
• Shortness of breath and nausea
• Weakness
• Burning pain in the hands or feet
• Dizziness or lightheadedness
• Fatigue
• Pain, swelling, and redness in your hands and feet

Less commonly, very high platelet levels may cause bleeding problems. This may sound unusual since thrombocytosis usually makes your blood clot. In this situation, unusual or excessive bleeding happens because the dramatic increase in blood clots uses up platelets in your bloodstream, leaving you without platelets to slow or stop bleeding^[3]. Bleeding symptoms can include^[1][7]:

• Nosebleeds
• Bruising easily
• Bleeding from your mouth or gums
• Bloody stool

What causes thrombocytosis?

The causes of thrombocytosis depend on which type you have.

Essential thrombocythemia is a genetic condition you develop in your lifetime. With essential thrombocythemia, some of the genes that tell your body how to make platelets change or mutate. As a result, your bone marrow—the spongy tissue inside your bones that contains stem cells—produces too many platelets^[7].

Reactive thrombocytosis happens when your body reacts to a condition or event by making too many platelets. Or your body may not get rid of old platelets fast enough, so too many build up in your blood^[7].

Some causes of reactive thrombocytosis include^[1][5][7]:

• Blood loss from recent surgery or injury
• Cancer and certain blood disorders
• Infections, especially bacterial infections that are severe or chronic
• Inflammatory disorders such as rheumatoid arthritis or inflammatory bowel disease
• Iron deficiency anemia
• Removal of your spleen
• Hemolytic anemia—a type of anemia in which your body destroys red blood cells faster than it produces them
• Some medications

How is thrombocytosis diagnosed?

A blood test called a complete blood count (CBC) can show if your platelet count is too high. A high platelet count means you have more than 450,000 platelets per microliter of blood^[1][7].

Your healthcare provider may order a follow-up blood test a few weeks later to see if your platelets stay high. Levels that return to normal aren’t usually concerning. If your levels stay high, your provider will need to learn which type of thrombocytosis you have. This helps them find the right treatments^[7].

You may also need blood tests to check for^[1][8]:

• High or low iron levels
• Markers of inflammation
• Undiagnosed cancer
• Gene mutations such as JAK2, CALR, or MPL

You might also need a procedure that uses a needle to remove a small sample of your bone marrow for testing. This is called a bone marrow biopsy^[1][8].

Treatment approaches

Treatment for thrombocytosis depends on which type you have and your individual risk factors.

Treatment for reactive thrombocytosis

Treatment for reactive thrombocytosis depends on the cause^[1][8]:

If you’ve had significant blood loss from a recent surgery or an injury, your elevated platelet count might resolve on its own as you recover.

If you have a chronic infection or an inflammatory disease, your platelet count likely will remain high until the condition is under control. In most cases, your platelet count will return to normal after the underlying cause is resolved.

If you’ve had your spleen removed, you might have lifelong thrombocytosis, but you’re unlikely to need treatment.

Treatment for essential thrombocythemia

People with essential thrombocythemia who have no signs or symptoms usually don’t need treatment. You might need to take daily, low-dose aspirin to help thin your blood if you’re at risk of blood clots. Don’t take aspirin without checking with your healthcare team^[1][8].

You might need to take prescription medicine or have procedures to lower your platelet counts if you^[8]:

• Have a history of blood clots and bleeding
• Have risk factors for heart disease
• Are older than 60
• Have a very high platelet count

Your doctor might prescribe platelet-lowering drugs such as hydroxyurea or anagrelide. These medications are used to reduce the number of platelets in your blood^[8][16].

Alpha-interferon is a natural substance often used as biological therapy to treat essential thrombocythemia^[16].

During plateletpheresis, a special machine filters the excess platelets out of the blood. This is usually done only when the platelet count is very high, and the effect is temporary^[16].

Possible complications

Complications are more common in essential thrombocythemia than in reactive thrombocytosis. The biggest concern is that blood clots can lead to a heart attack or stroke. But clots can form in other places too, like your lungs and legs^[7][9].

Essential thrombocythemia can lead to a variety of potentially life-threatening complications, such as^[1][6]:

• Strokes—if a blood clot occurs in the arteries that supply the brain
• Heart attacks—if blood clots occur in the arteries that supply blood to your heart
• Blood clots in the lungs (pulmonary embolism)

Sometimes, essential thrombocythemia can transform into leukemia or leave scarring inside your bones, a condition called myelofibrosis^[7].

Pregnant women with untreated essential thrombocythemia have an increased risk of pregnancy complications, including miscarriage, the baby developing slower than normal during pregnancy, and premature birth^[4]. Most women who have essential thrombocythemia have normal, healthy pregnancies. However, uncontrolled thrombocythemia can lead to complications. Your risk of pregnancy complications may be reduced with regular checkups and medication^[6].

Living with thrombocytosis

If you are diagnosed with thrombocytosis, it is important that you follow your treatment plan. Your healthcare provider will monitor your condition, and you may need procedures to manage complications^[15].

There are simple things you can do which may make a difference to how you feel, mentally and physically, after your diagnosis^[12]:

It’s good for everyone to drink plenty of fluids, but it’s particularly important if you have a high level of platelets. Healthcare recommendations suggest drinking 6 to 8 glasses of water or other low-fat and low-sugar drinks every day. Ask your hospital team to advise how much fluid you should be aiming to drink each day^[12].

Smoking increases your risk of blood clots. As thrombocytosis also increases this risk, it’s important for smokers with this condition to stop, or at least cut down^[12].

To help prevent complications, you may need to take steps such as^[15][16]:

• Avoid bumping or bruising yourself
• Use an electric razor, and be cautious when using nail trimmers, knives, and other sharp objects
• Wear hard-soled shoes, gloves, and long pants when working outside
• Use a sponge toothbrush if you have problems with gum bleeding
• Avoid aspirin or aspirin-like medications (for example, ibuprofen or other anti-inflammatory drugs) unless your doctor has told you otherwise, as these medications can affect platelet function

You may need routine tests to monitor your platelet levels. If you are taking medicines to lower your platelet count, tell your provider or dentist about them before any surgery or dental procedures. These medicines thin your blood and may increase bleeding during the procedure^[15].