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

Primary thrombocythemia is a disorder that slowly progresses. It 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.

The disease is in the same family of disorders as:

• Chronic myelogenous leukemia
• Myelofibrosis
• Polycythemia vera

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 well, bleeding is also a common problem.

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

The condition may even cause strokes in some people.

This condition is often detected on blood tests done for other reasons, before there are any symptoms.

A physical exam may show an enlarged spleen or liver.

Other tests may include:

• Bone marrow aspiration
• CBC
• Genetic tests
• Uric acid level

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

Long-term use of medications to decrease the platelet count can reduce both bleeding and clotting complications. The most commonly used medications include hydroxyurea, interferon-alpha, or anagrelide. In patients who have a tendency to clot, aspirin may help decrease clotting episodes.

Many patients do not need any treatment. However, the health care provider should monitor their condition.

The outcome varies. Most people go long periods of time without complications and have a normal life expectancy. In a very small minority of patients, complications from hemorrhage and thrombosis lead to death.

• Acute leukemia or myelofibrosis
• Severe hemorrhage
• Thrombotic episodes (stroke, heart attack, or blood clots in the 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

Tefferi A. Myeloproliferative disorders: Essential thrombocythemia and primary myelofibrosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 177.