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

From the Guidelines

Thrombocytosis is primarily caused by myeloproliferative neoplasms, such as essential thrombocythemia, and can also be secondary to various conditions including infections, inflammation, and malignancies. The causes of thrombocytosis can be categorized into primary and secondary, with primary thrombocytosis resulting from genetic mutations in bone marrow stem cells leading to autonomous platelet production 1. Secondary thrombocytosis occurs as a reaction to underlying conditions, including:

• Infections
• Inflammation
• Iron deficiency anemia
• Malignancies, such as lymphomas, leukemias, and solid tumors
• Tissue damage
• Post-splenectomy state
• Certain medications, such as epinephrine, vincristine, and corticosteroids

The mechanism behind thrombocytosis involves increased production of thrombopoietin and other cytokines that stimulate megakaryocyte proliferation and platelet production in the bone marrow 1. In essential thrombocythemia, the risk of thrombosis is increased, with a higher incidence of thrombosis reported in patients with a history of thrombotic events, age ≥ 65 years, and the presence of the JAK2V617F mutation 1.

Some conditions, such as Kawasaki disease, can also cause thrombocytosis, typically occurring in the second week of illness and peaking in the third week 1. The diagnosis and management of thrombocytosis depend on the underlying cause, and treatment may involve specific hematologic therapy or addressing the underlying condition.

In terms of risk factors for thrombosis in patients with myeloproliferative neoplasms, the International Prognostic Score of thrombosis for essential thrombocythemia (IPSET-thrombosis) is used to determine the risk of thrombosis, based on factors such as age, history of thrombosis, and the presence of the JAK2V617F mutation 1.

Overall, the management of thrombocytosis requires a comprehensive approach, taking into account the underlying cause and the risk of thrombosis, to minimize morbidity and mortality and improve quality of life.

From the Research

Causes of Thrombocytosis

• Thrombocytosis can be caused by primary or secondary events, with secondary thrombocytosis being more common, accounting for 83.1% of cases 2
• Primary thrombocytosis is often associated with myeloproliferative neoplasms (MPNs), such as essential thrombocythemia, polycythemia vera, and primary myelofibrosis 3, 4, 5
• Secondary thrombocytosis can be caused by various factors, including:
  • Tissue injury (32.2%) 2
  • Infection (17.1%) 2
  • Chronic inflammatory disorders (11.7%) 2
  • Iron deficiency anemia (11.1%) 2
  • Splenectomy 3
  • Solid tumors, such as lung cancer 3
• Genetic mutations, such as JAK2, CALR, and MPL, can also contribute to the development of thrombocytosis, particularly in cases of essential thrombocythemia 3, 4, 5

Risk Factors for Thrombocytosis

• Age older than 60 years 3, 4, 5
• History of thrombosis 3, 4, 5
• Presence of JAK2 gene variant 3, 4, 5
• Cardiovascular risk factors, such as hypertension, diabetes mellitus, hyperlipidemias, and tobacco use 3
• Extreme thrombocytosis 4
• Abnormal karyotype 4, 5