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Who Is at Risk for Thrombocythemia or Thrombocytosis?

Primary Thrombocythemia

Thrombocythemia isn't common. The exact number of people who have the condition isn't known. Some estimates suggest that 24 out of every 100,000 people have primary thrombocythemia.

Primary thrombocythemia is more common in people aged 50 to 70, but it can occur at any age. For unknown reasons, more women around the age of 30 have primary thrombocythemia than men of the same age.

Secondary Thrombocytosis

You might be at risk for secondary thrombocytosis if you have a disease, condition, or factor that can cause it. (For more information, go to "What Causes Thrombocythemia and Thrombocytosis?")

Secondary thrombocytosis is more common than primary thrombocythemia. Studies have shown that most people who have platelet counts over 500,000 have secondary thrombocytosis.

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Thrombocythemia and Thrombocytosis Clinical Trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for Thrombocythemia and Thrombocytosis, visit

July 31, 2012 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.