From the Guidelines
Thrombocytosis is primarily caused by myeloproliferative neoplasms (MPNs), such as polycythemia vera (PV) and essential thrombocythemia (ET) 1. These conditions are characterized by the overproduction of platelets in the bone marrow, leading to an excessive number of platelets in the blood. Other causes of thrombocytosis include reactive conditions, such as inflammation, infection, or iron deficiency anemia, which can stimulate the production of platelets 1.
- Primary thrombocytosis is often associated with MPNs, and the risk of thrombosis is increased in these patients, particularly in those with a history of thrombosis or advanced age 1.
- Secondary thrombocytosis is often caused by reactive conditions, and the treatment is focused on addressing the underlying cause.
- Risk factors for thrombosis in patients with thrombocytosis include advanced age, history of thrombosis, and the presence of cardiovascular risk factors, such as hypertension, diabetes mellitus, and smoking 1.
- Laboratory findings in patients with thrombocytosis may include elevated platelet counts, leukocytosis, and elevated acute-phase reactants, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) 1. Some studies suggest that leukocytosis may be a risk factor for thrombosis in patients with ET, particularly in those with a high white blood cell count 1. However, the relationship between platelet count and thrombotic risk is not well established, and some studies have reported that extreme thrombocytosis (platelet count >1,000 x 10^9/L) may be associated with a lower risk of thrombosis 1.
From the Research
Causes of Thrombocytosis
Thrombocytosis can be caused by various factors, including:
- Physiological mechanisms 2
- Pathological mechanisms 2
- Inflammatory states 2, 3
- Iron deficiency 2
- Recent surgery 2
- Underlying neoplasms 2, 4
- Myeloproliferative neoplasms, such as essential thrombocythaemia 2, 3, 4
- Genetic mutations affecting thrombopoiesis, such as JAK2 mutations 4
Types of Thrombocytosis
There are two principal types of thrombocytosis:
- Essential (primary) thrombocythemia, a myeloproliferative neoplasm associated with mutations of genes that regulate thrombopoiesis 4
- Reactive (secondary) thrombocytosis, frequently encountered in the family medicine setting, which rarely causes vascular complications or requires management beyond that required for the underlying condition 4
Underlying Conditions
Thrombocytosis can be associated with various underlying conditions, including: