Definition of Primary thrombocythemia:

Primary thrombocythemia is when the bone marrow is making too many platelets without a known cause. Platelets are essential for blood clotting.

Causes, incidence, and risk factors:

Primary thrombocythemia is a disorder that is caused by too much growth of a type of cell that is used to make blood cells. Although the platelets are mostly affected, the red blood cells and white blood cells may also be involved. This condition slowly gets worse over time.

The disease is in the same family of disorders as:

• Chronic myelogenous leukemia
• Polycythemia vera
• Primary myelofibrosis

Usually it affects people in middle age. It can also be seen in younger patients, especially females under age 40.

People with this condition make too many platelets and may have a problem with blood clots (thrombosis). Because these platelets do not work normally, bleeding is also a common problem.