Thrombocytosis is a raised number of platelets, usually defined as ≥ 450 x 10^9
Thrombocytosis may be divided into :
- Spurious
- Caused by non-platelet structures in the blood which are counted as platelets by modern automated counters
- Examples include
- Cryoglobulin crystals
- Microspherocytes (eg from severe burns)
- Schistocytes
- Pappenheimer bodies
- Bacteria
- Primary thrombocytosis
- Increase in platelets caused by alterations targeting the haematopoietic cells
- Causes are
- Essential thrombocytheameia
- Megakaryocyte proliferation
- Not meeting WHO criteria for CML, PV, PMF or MDS
- Presence of JAK 2 or other clonal marker and no evidence of reactive thrombocytosis
- Increases risk of both thrombosis and bleeding
- Treatment:
- High risk patients (aged >60 OR platelet count >1500 OR disease-related thrombotis/haemorrhage)
- Hydroxycarbamide plus aspirin
- ? interferon alpha in young patients
- Other patients
- Aspirin only
- Polycythaemia Vera
- Myelofibrosis
- Chronic myeloid leukaemia
- Secondary/reactive thrombocytosis
- Reactive to
- Infection
- Inflammation
- Post-operative/trauma
- Iron deficiency
- Hyposplenism
- Haemorrhage
- Malignancy
- Drugs
- Corticosteroids
- Adrenaline
- Rarely causes complications
- Treat underlying cause
Small print gem: extremely high platelet levels (>1500 x 10^9) result in more causes of bleeding than thrombosis
