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Essential Thrombocytosis Treatment & Management

  • Author: Asheesh Lal, MBBS, MD; Chief Editor: Emmanuel C Besa, MD  more...
Updated: Nov 06, 2015

Medical Care

Treatment in patients with essential thrombocytosis (primary thrombocythemia) should be individualized on the basis of risk factors for thrombohemorrhagic complications. Risk factors include the following:

  • Age 60 years or older
  • History of thrombosis
  • Platelet count greater than 1500 x 10 9/L (1.5 million/µL), which is paradoxically associated with an increased risk of gastrointestinal tract bleeding in young women
  • Obesity
  • Cardiovascular risk factors such as smoking, hypertension, and hypercholesterolemia
  • Markers of hypercoagulability such as factor V Leiden and antiphospholipid antibodies [4]

Observation may be appropriate for low-risk patients (ie, those lacking any of the above risk factors). Low-risk patients experience lower rates of thrombosis or bleeding. Generally, significantly increased thrombohemorrhagic risk is not associated with surgery or pregnancy in low-risk patients. Alternatively, low-risk patients may be treated with low-dose aspirin. In addition, low-dose aspirin may be useful in treating patients with symptoms of microvascular occlusion (eg, erythromelalgia).

In emergencies, plateletpheresis may be useful to achieve a rapid decrease in platelet counts in the setting of acute thrombosis and/or marked thrombocytosis.

Cytoreductive therapy should be used to decrease the platelet count in high-risk patients (eg, those over 60 years of age, those with a history of thrombosis, or platelet counts greater than 1.5 million/µL). Low-dose aspirin with cytoreductive therapy or observation may help treat intermediate-risk patients (ie, those who do not fit into either high-risk or low-risk groups).

Lifestyle modifications should be recommended for all patients with reversible risk factors. These include diet and exercise to promote weight loss for obese patients and smoking cessation for smokers.

Cytoreductive therapy

Cytoreductive therapy is used to reduce the risk of hemorrhage for patients with platelet counts above 1 million/μL. Extreme thrombocytosis may promote the abnormal adsorption of large von Willebrand factor (VWF) multimers. These patients should be screened for the presence of acquired von Willebrand disease (VWD). Low-dose aspirin therapy (eg, ≤100 mg/day) is acceptable if the ristocetin cofactor level is at least 30% in absence of other high risk factors; if it is less than 30%, all aspirin should be avoided.

Cytoreductive drugs that are commonly used for essential thrombocytosis include the following:

  • Hydroxyurea, [6, 27]
  • Anagrelide [27]
  • Interferon alfa
  • Phosphorus-32 ( 32 P)

A randomized study comparing hydroxyurea versus observation in patients at high risk for thrombosis showed a marked decrease in the number of thrombotic episodes in the hydroxyurea arm.[6] Another randomized study that compared hydroxyurea plus aspirin with anagrelide plus aspirin found that in high-risk patients (previous thrombosis, age >60 y or platelets >1000 x 109/L), treatment with anagrelide plus aspirin was associated with increased rates of arterial thrombosis, major hemorrhage, and myelofibrotic transformation, but a decreased rate of venous thromboembolism.[27]

The reason for the higher rate of myelofibrosis in patients receiving anagrelide remains unclear. This finding may be the result of increased production of profibrotic cytokines with anagrelide, or may simply represent the natural course of essential thrombocytosis.

In view of those studies, hydroxyurea should be considered as cytoreductive agent of choice for most high-risk patients with essential thrombocytosis. Further choice of the cytoreductive agent should also be based on patient factors (eg, age, child-bearing potential, cost, life expectancy, comorbidities). A combination of cytoreductive agents may be needed in cases difficult to manage by single-agent therapy.

Interferon alfa produces high rates of clinical and molecular responses in patients with JAK2 or CALR mutations.[28, 29] Italian guidelines recommend interferon alfa as a first-line platelet-lowering therapy for patients younger than 40 years, male or female, who have no childbearing potential.[30] Interferon alfa may also be used as second-line therapy in older patients.[31]

In emergencies, plateletpheresis may be useful to achieve a rapid decrease in platelet counts. Plateletphersis may be indicated in the setting of acute thrombosis and/or marked thrombocytosis.

The investigational drug imetelstat, a telomerase inhibitor, has shown promise in the treatment of essential thrombocytosis. In a phase II trial that included18 patients in whom prior treatments had been ineffective or had caused unacceptable side effects from, all 18 had hematologic responses, and 16 patients had a complete hematologic response; most patients also demonstrated a molecular response.[32]


Surgical Care

Patients with essential thrombocytosis (primary thrombocythemia) undergoing surgery are at increased risk for bleeding and thrombosis. Administer cytoreductive therapy to decrease the platelet count to the reference range before surgery. Avoid splenectomy because it can markedly increase the platelet count and the risk of both hemorrhagic and thrombotic events.



A hematologist can help manage patients with essential thrombocytosis as well as monitor the cytoreductive therapy.

Contributor Information and Disclosures

Asheesh Lal, MBBS, MD Physician, Department of Internal Medicine, Lexington Medical Center

Asheesh Lal, MBBS, MD is a member of the following medical societies: American Society of Clinical Oncology, American Society of Hematology

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Marcel E Conrad, MD Distinguished Professor of Medicine (Retired), University of South Alabama College of Medicine

Marcel E Conrad, MD is a member of the following medical societies: Alpha Omega Alpha, American Association for the Advancement of Science, American Association of Blood Banks, American Chemical Society, American College of Physicians, American Physiological Society, American Society for Clinical Investigation, American Society of Hematology, Association of American Physicians, Association of Military Surgeons of the US, International Society of Hematology, Society for Experimental Biology and Medicine, SWOG

Disclosure: Partner received none from No financial interests for none.

Chief Editor

Emmanuel C Besa, MD Professor Emeritus, Department of Medicine, Division of Hematologic Malignancies and Hematopoietic Stem Cell Transplantation, Kimmel Cancer Center, Jefferson Medical College of Thomas Jefferson University

Emmanuel C Besa, MD is a member of the following medical societies: American Association for Cancer Education, American Society of Clinical Oncology, American College of Clinical Pharmacology, American Federation for Medical Research, American Society of Hematology, New York Academy of Sciences

Disclosure: Nothing to disclose.


Wadie F Bahou, MD Chief, Division of Hematology, Hematology/Oncology Fellowship Director, Professor, Department of Internal Medicine, State University of New York at Stony Brook

Wadie F Bahou, MD is a member of the following medical societies: American Society of Hematology

Disclosure: Nothing to disclose.

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Peripheral blood smear in essential thrombocytosis showing increased platelet numbers. Courtesy Wei Wang, MD, and John Lazarchick, MD; Department of Pathology, Medical University of South Carolina.
Bone marrow biopsy in essential thrombocytosis showing increased megakaryocytes. Courtesy Wei Wang, MD, and John Lazarchick, MD; Department of Pathology, Medical University of South Carolina.
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