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 reactive conditions 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. These conditions are characterized by the overproduction of platelets in the bone marrow, leading to elevated platelet counts in the blood.

Some of the key factors that contribute to thrombocytosis in myeloproliferative neoplasms include:

• Age ≥ 65 years
• Prior thrombosis
• Leukocytosis
• JAK2V617F mutation
• Cardiovascular risk factors, such as hypertension, diabetes mellitus, and smoking

In addition to myeloproliferative neoplasms, other conditions can also cause thrombocytosis, including:

• Infections
• Inflammation
• Iron deficiency anemia
• Cancer
• Recent surgery
• Certain medications
• Stress
• Exercise
• Pregnancy

It is essential to distinguish between primary and secondary thrombocytosis, as the underlying causes and treatment approaches differ significantly. Primary thrombocytosis, such as ET and PV, often requires specific hematologic treatments to reduce platelet counts and prevent clotting complications, whereas secondary thrombocytosis typically resolves when the underlying cause is addressed 1.

From the Research

Causes of Thrombocytosis

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

• Physiological mechanisms 2
• Pathological mechanisms 2
• Inflammatory states 2, 3, 4
• Iron deficiency 2, 3, 4
• Recent surgery 2
• Underlying neoplasms 2, 3, 4, 5, 6
• Myeloproliferative neoplasms, such as essential thrombocythemia, polycythemia vera, and myelofibrosis 2, 3, 4, 5, 6
• Gene mutations, including JAK2, CALR, and MPL 5, 6
• Tissue injury 3
• Infection 3, 4
• Chronic inflammatory disorders 3
• Solid tumors, such as lung cancer 5

Classification of Thrombocytosis

Thrombocytosis can be classified into two main types:

• Primary thrombocytosis, which is caused by myeloproliferative neoplasms 3, 4, 5, 6
• Secondary thrombocytosis, which is caused by other factors, such as inflammation, infection, or iron deficiency 2, 3, 4

Clinical Characteristics

Patients with thrombocytosis may present with various clinical characteristics, including:

• Elevated platelet count 2, 3, 4, 5, 6
• Thrombotic complications 2, 3, 4, 5, 6
• Bleeding events 4, 5, 6
• Splenomegaly 6
• Leukocytosis 6
• Vasomotor disturbances 6
• Pruritus 6