From the Guidelines

Thrombocytosis is primarily caused by myeloproliferative neoplasms (MPNs), such as polycythemia vera (PV) and essential thrombocythemia (ET) 1.

Myeloproliferative neoplasms (MPNs): MPNs, including PV and ET, are characterized by the overproduction of platelets, leading to thrombocytosis 1.
Reactive thrombocytosis: This occurs in response to inflammation, infection, or other conditions, such as Kawasaki disease 1.
Iron deficiency: Iron deficiency can lead to an increase in platelet production, resulting in thrombocytosis.
Splenectomy: Removal of the spleen can lead to an increase in platelet count, as the spleen normally removes old or damaged platelets from the circulation.

Leukocytosis: An increase in white blood cell count is often associated with MPNs and can contribute to thrombocytosis 1.
JAK2V617F mutation: This mutation is commonly found in MPNs and can contribute to thrombocytosis 1.
Hormonal factors: Hormonal changes, such as those that occur during pregnancy, can increase the risk of thrombocytosis 1.
Inherited thrombophilias: Certain genetic mutations, such as factor V Leiden, can increase the risk of thrombocytosis 1. It is essential to note that the causes of thrombocytosis can vary depending on the individual and the underlying condition. A thorough evaluation and diagnosis by a healthcare professional are necessary to determine the underlying cause of thrombocytosis.

From the Research

Thrombocytosis can be caused by a variety of factors, including:

Primary thrombocytosis, which is often due to essential thrombocythemia (ET) or other myeloproliferative disorders (MPDs) 2
Secondary thrombocytosis, which can be caused by:
- Infections, such as bacterial or viral infections 3, 4, 5
- Tissue injury or damage 4, 5
- Chronic inflammatory disorders, such as rheumatoid arthritis or inflammatory bowel disease 4, 5
- Iron deficiency anemia 4
- Malignancy or cancer 5
- Rebound thrombocytosis, which can occur after a period of thrombocytopenia 5
- Postsplenectomy patients 5

Thrombocytosis can be classified as:

Primary thrombocytosis, which is further divided into:
- Familial thrombocytosis
- Essential thrombocytosis (ET)
Secondary thrombocytosis, which is also known as reactive thrombocytosis (RT) 6

Patients with thrombocytosis may present with:

Elevated platelet count, which can be mild, moderate, or severe 6
Clinical characteristics such as fever, tachycardia, weight loss, hypoalbuminemia, neutrophilia, leukocytosis, and anemia 3
Increased risk of thrombosis or bleeding complications, particularly in patients with primary thrombocytosis 2, 4