Thrombocytosis

Thrombocytosis is a high platelet count. Platelets are blood cells that stop bleeding by sticking together to form a clot. But too many platelets can sometimes make your blood too sticky. In serious cases, they can cause harmful blood clots. Without treatment, these clots can lead to a heart attack or stroke.

Types of thrombocytosis

There are two main types:

• Reactive thrombocytosis (secondary): This is when a high platelet count is a response to something else, like an infection or surgery. It’s the most common type and is usually temporary.
• Essential thrombocytosis (primary): Less often, high platelet counts happen when your bone marrow (the site of blood cell production) makes too many abnormal platelets.

Either way, think of thrombocytosis as a sign that something’s going on inside your body that your healthcare provider needs to learn more about. Based on what they find, you may need long-term treatments, short-term treatments or no treatment at all.

Symptoms of thrombocytosis

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.

Thrombocytosis that leads to clots or (rarely) bleeding inside your body can cause noticeable changes. This is more common with essential thrombocytosis. Symptoms include:

• Fatigue
• Nosebleeds
• Bruising easily
• Bleeding easily from your mouth or gums
• Dizziness, lightheadedness and headaches
• Pain, swelling and redness in your hands and feet (a sign of erythromelagia)
• Pain in your abdomen, especially the upper right side (a sign of Budd-Chiari syndrome)

Thrombocytosis causes

Essential thrombocytosis (ET) is a genetic condition you develop in your lifetime. With ET, some of the genes that tell your body how to make platelets change (mutate). As a result, your bone marrow makes too many of them.

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.

These are just some causes of a high platelet count:

• Blood loss
• Cancer
• Infections
• Inflammatory conditions
• Iron-deficiency anemia
• Some medications
• Spleen removal surgery

Complications of this condition

Complications are more common in essential thrombocytosis (ET) than in reactive thrombocytosis. The biggest concern is that clots can lead to a heart attack or stroke. But clots can form in other places, too, like your lungs and legs.

Sometimes, ET can transform into leukemia or leave scarring inside your bones (a condition called myelofibrosis). It may increase your chances of problems during pregnancy.

Your healthcare team will keep close tabs on your health if you have ET. They’ll work to prevent complications. If prevention isn’t possible, they’ll ensure you get the treatment you need ASAP.

How doctors diagnose this condition

Healthcare providers diagnose thrombocytosis based on blood test results. A high platelet count means you have more than 450,000 platelets per microliter of blood. Your 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 the type of thrombocytosis. This helps them find the right treatments. Tests may include:

• More blood tests: Providers look for signs of conditions that cause thrombocytosis. They may check for abnormal iron levels or signs of inflammation. They may search for odd-looking platelets.
• Genetic tests: These show if you have mutations common in essential thrombocytosis. Most people with ET have mutations in one of the following genes: JAK2, CALR1 or MPL1.
• Bone marrow biopsy: This test checks for abnormal platelets in your bone marrow. It can confirm you have ET.

How is thrombocytosis treated?

Reactive thrombocytosis often gets better on its own. If not, levels usually return to normal once you get treatment for what’s causing your high platelet counts.

There’s no cure for essential thrombocytosis. But your healthcare provider can help you manage it and reduce your risk of clots. Treatment options include:

• Watchful waiting: If you don’t have symptoms, your provider may monitor you. They’ll recommend treatment only if you need it.
• Low-dose aspirin: You may need to take a daily aspirin to prevent blood clots. Be sure to check with your provider before taking aspirin regularly.
• Medicines that lower platelet levels: Medications include hydroxyurea, anagrelide and interferon alfa.
• A procedure to remove your platelets: Your provider may filter excess platelets from your blood to prevent life-threatening clots.

When should I see my healthcare provider?

Follow your provider’s guidance on how often you’ll need blood work to check your platelet count. Ask them how to recognize the changes in your body that let you know it’s time to get your levels checked.

Seek emergency care if you notice signs of a stroke or heart attack.

What can I expect if I have thrombocytosis?

The most common causes of thrombocytosis are short-lived and don’t put you at risk of serious blood clots. With reactive thrombocytosis, things usually improve on their own or once you get treated. The outlook is more complex if a chronic condition (like cancer) is causing it. The underlying cause of thrombocytosis plays the biggest role in shaping what comes next.

If you have essential thrombocytosis, your healthcare provider will work with you to manage your platelet counts. You may need to take new medications. And you may need to plan for regular visits with your provider. They’ll advise you on what to do.

Is thrombocytosis serious?

It can be. A lot depends on what’s causing your high platelet count. For example, thrombocytosis related to an infection may go away after your body fights off the bug that caused it. Thrombocytosis related to your genes isn’t curable. But it may not cause major issues at all. Or it may increase your risk of harmful blood clots.

There are no definite answers. This is why your healthcare provider is your best resource for explaining what your blood test results mean.

Can high platelets make you feel ill?

Sometimes. When a clot forms in your body, it can prevent blood from reaching tissue. This can cause lots of symptoms depending on the clot. You may feel fatigued, nauseated or just unwell. But not all clots cause the same effects.