A high platelet count indicates too many of the small cells (platelets) that help form blood clots.
This can cause dangerous clots and bleeding.
Reactive thrombocytosisis because of an underlying condition like:
Essential thrombocythemiadescribes platelet counts rising independently due tobone marrowdysfunction.
Illustration by Michela Buttignol for Verywell Health
Regardless of the cause, a high platelet count can result in dangerous blood clots and bleeding.
For this reason, many people are diagnosed with these conditions after a routine blood test.
RT is the more common cause of a high platelet count.
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With RT, platelet counts are high because of an underlying event or disease.
Additional testing may be ordered to determine whether high platelets are because of an infection or other condition.
Chronic Inflammatory Diseases
Inflammation is the body’s natural response to an infection or injury.
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Chronic or long-term inflammation is a feature of conditions likechronic obstructive pulmonary disease(COPD) andmyocarditis.
Autoimmune conditions also cause chronic inflammation.
When you have an autoimmune condition, your immune system mistakenly attacks your body’s own tissues.
Allergic Conditions
Allergy and atopic (allergy-related) diseases can also cause RT.
For reasons that are not entirely clear, platelet counts will commonly rise when this occurs.
Again, scientists are not entirely sure why platelets increase as the red blood count decreases.
Asplenia
Aspleniais the lack of aspleen.
These increases can be extreme when a cancer hasmetastasized(spread to distant parts of the body).
Paraneoplastic thrombocytosis can occur with all types of cancer but is more common in some cancers than others.
With essential thrombocythemia, too many platelets are produced.
ET is a slowly progressive disease with long periods with no symptoms.
In rare instances, ET can progress toacute myeloid leukemia (AML).
ET is more common in older adults, especially females, and is rarely seen in children.
Treating Thrombocytosis
Reactive thrombocytosisrarely requires treatment.
Complications of a High Platelet Count
Thrombocytosis and thrombocythemia can cause serious complications such as blood clots.
Blood clots can restrict blood flow to your organs, including your brain and heart.
This can happen when blood clots use too many of the platelets in your body.
Bleeding can also occur if you have abnormal platelets that don’t clot the way they are supposed to.
Summary
A high blood platelet count sparked by an underlying condition is known as reactive thrombocytosis.
In many cases, RT is asymptomatic and may resolve naturally.
Less common essential thrombocythemia is a high platelet count because of bone marrow dysfunction.
This condition has no cure but can be effectively managed to lower the risk of developing blood clots.
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