Essential Thrombocythaemia

Uncontrolled production of abnormal platelets

Aetiology

  • Median age of diagnosis ~65 but can affect younger patients

Pathophysiology

  • Platelet function is abnormal
    • Thrombosis
    • At high levels can also cause bleeding due to acquired von Willebrand disease

Clinical presentation

  • Asymptomatic
  • Increased cellular turnover - gout, fatigue, weight loss, sweats
  • Symptoms/signs due to splenomegaly
  • Marrow failure - fibrosis or leukaemic transformation (transformation risk is low)
  • Thrombosis - arterial or venous including TIA, MI, abdominal vessel thrombosis, claudication, erythromelalgia
  • Bleeding - unpredictable risk

Investigations

  • Exclude reactive thrombocytosis - blood loss, inflammation, malignancy, iron deficiency
  • Exclude CML
  • Genetics:
    • JAK2 mutations in approx. 50-60%
    • CALR mutation in approx 25%
    • MLP mutation in approx 5%
    • 10-20% of patients will be ‘triple negative’
  • Characteristic bone marrow appearances

Management

  • Antiplatelet agents - aspirin
  • Cytoreductive therapy to control proliferation - hydroxycarbamide, anagrelide, interferon alpha