Primary thrombocythemia is the overproduction of platelets without a recognizable cause. Platelets are essential for blood clotting.

Primary thrombocythemia is a slowly progressing disorder, caused by overgrowth of a type of cell that is a precursor of blood cells. Although the platelets are primarily affected, the red blood cells and white blood cells are also involved.

The disease has similarities to polycythemia vera, chronic myelogenous leukemia, and myelofibrosis. Usually it affects people in middle age. Bleeding can occur from the gastrointestinal tract, respiratory system, urinary tract, or skin.

The formation of blood clots (thrombosis), may occur with bleeding episodes. It may even cause strokes in some people. Risk factors are unknown. The incidence is about 3 out of 100,000 people.

• Bleeding from the gastrointestinal tract
• Bleeding from the gums
• Bloody stools
• Dizziness
• Easy bruising
• Enlarged lymph nodes (rare)
• Headache
• Nosebleeds (epistaxis)
• Numbness of hands or feet
• Prolonged bleeding from surgical procedures or tooth extraction
• Ulcers on fingers or toes

• Bone marrow aspiration
• CBC that shows elevated platelet count
• Physical examination may show enlarged spleen or liver
• Uric acid level may be elevated

If a patient has life-threatening complications, platelet pheresis, a procedure to remove platelets from the blood directly, can rapidly decrease the platelet count.

Long-term decrease of the platelet count using medications can reduce both bleeding and clotting complications. Most common medications include hydroxyurea, interferon-alpha, or anagrelide. For patients with a known clotting tendency, aspirin may help decrease clotting episodes.

Some patients do not need any treatment.

The outcome varies. Some people have prolonged periods without complications, while complications related to hemorrhage and thrombosis lead to death in others.

• Acute leukemia or myelofibrosis can develop in some patients
• Severe hemorrhage
• Thrombotic episodes (stroke, heart attack, or blood clots in extremities)

Call your health care provider:

• If unexplained or prolonged bleeding occurs
• If chest pain, leg pain, confusion, weakness, numbness, or other new symptoms develop

Hoffman R, Benz Jr. EJ, Shattil SJ, et al., eds. Hematology: Basic Principles and Practice. 4th ed. Philladelphia, Pa: Churchill Livingston; 2005:1277-91.

Rakel RE. Textbook of Family Practice. 6th ed. Philadelphia, Pa: WB Saunders; 2002:1256.