What causes thrombocytosis (elevated platelet count)?

From the Guidelines

Thrombocytosis is primarily caused by myeloproliferative neoplasms, such as essential thrombocythemia (ET) and polycythemia vera (PV), as well as secondary factors like inflammation, infection, and iron deficiency anemia. According to a recent study published in the American Journal of Hematology 1, myeloproliferative neoplasms are a major cause of thrombocytosis, with ET and PV being the most common types. The study highlights that leukocytosis and JAK2V617F mutation contribute to thrombotic tendency in both ET and PV.

Some key factors that contribute to thrombocytosis include:

• Genetic mutations in blood stem cells, such as JAK2V617F mutation
• Inflammation and infection, which can stimulate the production of thrombopoietin, a hormone that promotes platelet production
• Iron deficiency anemia, which can lead to increased platelet production as a compensatory mechanism
• Certain medications, such as epinephrine and vincristine, which can stimulate platelet production
• Recent surgery or removal of the spleen, which can lead to increased platelet production as part of the body's healing response

It is essential to note that the underlying cause of thrombocytosis determines the treatment approach. For secondary thrombocytosis, addressing the underlying condition is crucial, while primary thrombocytosis may require medications to reduce platelet production, such as hydroxyurea, anagrelide, or interferon-alpha, along with low-dose aspirin to prevent clotting complications in high-risk patients 1.

From the Research

Causes of Thrombocytosis

Thrombocytosis, or elevated platelet count, can be caused by various conditions, including:

• Primary thrombocytosis, which is a myeloproliferative neoplasm (MPN) such as essential thrombocythemia (ET) 2, 3, 4, 5, 6
• Secondary thrombocytosis, which can be caused by:
  • Inflammation 3, 4, 5
  • Infection 3, 4, 5
  • Malignancy 3, 4, 5
  • Iron deficiency anemia 4, 5
  • Tissue injury 4
  • Asplenia 3
  • Chronic inflammatory disorders 4
  • Exposure to high altitude 3

Diagnostic Approach

The diagnostic approach to thrombocytosis involves:

• Excluding spurious thrombocytosis caused by microspherocytes, schistocytes, cryoglobulins, or bacteria 3
• Identifying the underlying cause of thrombocytosis, whether primary or secondary 2, 3, 4, 5, 6
• Stratifying patients according to their individual thrombotic and bleeding risk 2

Clinical Characteristics

The clinical characteristics of thrombocytosis can vary depending on the underlying cause, but may include:

• Thrombosis 2, 3, 4, 5, 6
• Bleeding events 2, 3, 5, 6
• Splenomegaly 6
• Qualitative platelet abnormalities 6