Platelet

Thrombocytosis

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Thrombocytosis, Thrombocythemia

  • See Also
  1. Thrombocytopenia
  2. Platelet Count
  • Definitions
  1. Thrombocytosis
    1. Increased Platelet Count >450,000/uL
  2. Extreme Thrombocytosis
    1. Increased Platelet Count >1,000,000/uL
  3. Spurious Thrombocytosis
    1. Incorrect transiently high automated Platelet Count reading (machine counts small non-Platelet particles)
    2. Confirm Thrombocytosis with a manual Platelet counr
  • Epidemiology
  1. Prevalence in adults: 1-2% (extreme in <1% of adults)
  • Causes
  1. Primary Thrombocytosis
    1. Essential Thrombocythemia
    2. Myelodysplastic Syndrome
    3. Hereditary Thrombocytosis
    4. Myelofibrosis or myeloid metaplasia
    5. Primary Myelofibrosis
    6. Polycythemia Vera
    7. Chronic Myelogenous Leukemia
  2. Secondary Thrombocytosis (>80% of cases)
    1. See Reactive Thrombocytosis
  • Labs
  • Initial after Thrombocytosis Identified
  1. Repeat Complete Blood Count with Platelet Count
  2. Peripheral Blood Smear
  3. C-Reactive Protein
  4. Iron studies including Ferritin
  • Evaluation
  1. Iron Deficiency Anemia identified
    1. Treat Iron Deficiency
    2. Recheck Complete Blood Count after treatment
  2. Reactive Thrombocytosis
    1. Evaluate for underlying cause (e.g. infection, inflammation)
    2. Consider chronic inflammatory conditions
    3. Repeat Complete Blood Count
  3. Persistent Thrombocytosis (Reactive Thrombocytosis and Iron Deficiency excluded)
    1. Consult hematology for primary Thrombocytosis
  • References
  1. Williams (2026) Am Fam Physician 113(4): 332-8 [PubMed]