What are the causes of thrombocytosis (increased platelet count)?

From the Guidelines

Thrombocytosis, or an increased platelet count, is primarily caused by myeloproliferative neoplasms, such as essential thrombocythemia (ET) and polycythemia vera (PV), as well as reactive causes like inflammation, infection, and iron deficiency anemia. The causes of thrombocytosis can be broadly categorized into primary and secondary thrombocytosis. Primary thrombocytosis is often associated with bone marrow disorders, including myeloproliferative neoplasms like ET and PV, as discussed in a recent study published in the American Journal of Hematology 1. Some key points to consider when evaluating the causes of thrombocytosis include:

• Myeloproliferative neoplasms, such as ET and PV, are primary causes of thrombocytosis, with a higher risk of thrombotic events associated with these conditions 1
• Reactive causes, such as inflammation, infection, and iron deficiency anemia, can also lead to secondary thrombocytosis
• Other factors, including splenectomy and certain medications like epinephrine, vincristine, and all-trans retinoic acid, can contribute to elevated platelet counts
• The risk of thrombosis in patients with ET or PV is influenced by factors such as age, prior thrombosis, leukocytosis, and the presence of JAK2V617F mutation, as highlighted in a recent meta-analysis 1
• The International Prognostic Score of thrombosis for ET (IPSET-thrombosis) is a useful tool for determining thrombotic risk in patients with ET, taking into account factors like age, thrombosis history, JAK2V617F mutation, and cardiovascular risk factors 1. In clinical practice, it is essential to identify the underlying cause of thrombocytosis and manage it accordingly, with a focus on reducing the risk of thrombotic complications and improving patient outcomes.

From the Research

Causes of Thrombocytosis

Thrombocytosis, or an increased platelet count, can be caused by various factors, including:

• Primary thrombocytosis, which is often associated with myeloproliferative neoplasms (MPNs) such as essential thrombocythemia, polycythemia vera, and primary myelofibrosis 2, 3, 4
• Secondary thrombocytosis, which can be caused by:
  • Tissue injury 2
  • Infection 2, 5
  • Chronic inflammatory disorders 2
  • Iron deficiency anemia 2, 5
  • Trauma or surgical intervention 5
  • Splenectomy 3
  • Solid tumors such as lung cancer 3
• Familial thrombocytosis, which is a rare condition caused by genetic mutations 4
• Reactive or secondary thrombocytosis, which can be caused by various systemic conditions 4, 6

Classification of Thrombocytosis

Thrombocytosis can be classified into two main types:

• Primary thrombocytosis, which is caused by a clonal myeloproliferative neoplasm 2, 3
• Secondary thrombocytosis, which is caused by a non-clonal condition such as infection, inflammation, or tissue injury 2, 5

Clinical Manifestations

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

• Thrombotic complications, such as arterial or venous thrombosis 2, 3
• Hemorrhagic complications, such as bleeding or bruising 3
• Splenomegaly, or enlargement of the spleen 3, 6
• Qualitative platelet abnormalities, such as impaired platelet function 6