Who Is At Risk for Thrombocythemia or Thrombocytosis?

Primary Thrombocythemia

This condition isn't common. The exact number of people who have the condition isn't known. Some estimates suggest that 1 to 2.5 out of every 100,000 people have primary thrombocythemia. This number may be low, because most people who have the condition don't have symptoms. Therefore, they may not know they have it.

Primary thrombocythemia occurs mostly between the ages of 50 and 70, but it can occur at any age. For unknown reasons, a higher number of women around the age of 30 have primary thrombocythemia than men of the same age.

Secondary Thrombocytosis

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

This condition is more common than primary thrombocythemia. In two studies of people with high platelet levels, most people with platelet counts over 500,000 had secondary thrombocytosis.