see also:

• full blood examination (FBE)
• thrombocytopenia

• thrombocytosis is defined by an excessive concentration of platelets in the peripheral blood > 500 x 10^9/L
• primary thrombocytosis may cause increased risk of thrombosis and stroke (CVA) and thus high risk patients are usually treated with long term hydroxyurea
• platelet count greater than 1.5 million x 10^9/L, is paradoxically associated with an increased risk of gastrointestinal tract bleeding in young women

• aka essential thrombocytosis
• a nonreactive, chronic myeloproliferative disorder
• clinical features:
  • platelet count > 600
  • megakaryocytic hyperplasia
  • splenomegaly
  • a clinical course complicated by thrombotic and/or haemorrhagic episodes

• usually asymptomatic and of no consequence
• part of the acute phase response to stress such as:
  • systemic infections
  • inflammatory conditions such as polyarteritis nodosa (PAN), inflammatory bowel disease (IBD)
  • haemorrhage
  • tumours