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

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Causes

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.

Symptoms

• Bleeding from the gastrointestinal tract, respiratory system, urinary tract, or skin
• Bleeding from the gums
• Bleeding (prolonged) from surgical procedures or tooth removal
• Bloody stools
• Dizziness
• Easy bruising
• Headache
• Nosebleeds (epistaxis)
• Numbness of the hands or feet
• Ulcers on the fingers or toes

The condition may even cause strokes in some people.

Exams and Tests

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. There may be abnormal blood flow in the toes or feet, as well as skin damage caused by that abnormal blood flow.

Other tests may include:

• Bone marrow aspiration and biopsy
• CBC
• Genetic tests (to look for a change in the JAK2 gene)
• Uric acid level

Treatment

If a patient has life-threatening complications, a procedure to remove platelets directly from the blood (platelet pheresis) can quickly 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 are at high risk for clotting (older patients, those with very high platelet levels or who have had past clotting episodes), aspirin at a low dose (81 to 100 mg per day) decreases clotting episodes.

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

Outlook (Prognosis)

The outcome varies. Most people go long periods of time without complications and have a normal life expectancy. In a very small number of patients, complications from bleeding (hemorrhage) and blood clots (thrombosis) can cause serious problems.

In a small number of patients, the disease will change into acute leukemia or myelofibrosis.

Possible Complications

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

When to Contact a Medical Professional

Call your health care provider:

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

Alternative Names

Essential thrombocythemia; Essential thrombocytosis

References

Finazzi G, Xu M, Barbui T, Hoffman R. Essential thrombocythemia. In: Hoffman R, Benz EJ Jr., Shattil SJ, et al, eds. Hoffman Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Churchill Livingstone Elsevier;2008:chap 127.

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.

Update Date: 2/28/2012

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.