Thrombocytosis

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Background

  • Defined as a platelet count >450,000/microL.

Reactive thrombocytosis (RT)

  • Most common cause of thrombocytosis, accounting for 85% of cases.
  • A reaction to another process, such as inflammation, infection, cancer, or iron deficiency.
  • Rarely causes complications even with extremely elevated platelet counts (>1,000,000/microL).

Autonomous thrombocytosis (AT)[1]

  • Accounts for 15% of cases
  • A primary problem that results from myeloproliferative disorders or myelodysplastic syndromes, such as essential thrombocytopenia or polycythemia vera.
  • Complications, such as bleeding and/or thrombosis, are more likely with AT than with RT so it is clinically important to differentiate reactive thrombocytosis versus autonomous thrombocytosis.
  • There are no diagnostic studies to differentiate RT versus AT.

Clinical Features[2]

Generally asymptomatic and found on routine lab testing; complications are typically from AT disorders

Differential Diagnosis[3]

Reactive thrombocytosis

Autonomous thrombocytosis

Spurious (false) thrombocytosis

  • Mixed cryoglobulinemia
  • Cytoplasmic fragments
  • Bacteremia

Evaluation

Workup

  • Labs
    • CBC, ESR, CRP, iron studies, LDH
  • CXR
  • Fecal occult blood test

Diagnosis

  • platelet count >450,000/microL.

Management

Reactive thrombocytosis

  • Treat underlying disease.

Autonomous thrombocytosis

Asymptomatic

  • 81mg ASA PO daily.
  • If high risk for thrombotic event (>60 yrs, history of thrombosis, or known JAK2 mutation), consider 15mg/kg hydroxyurea PO daily. Consult if available.
  • Second line agents include interferon-α, anagrelide, and pipobroman.

Thrombosis due to AT

  • Anticoagulation with LMWH.
  • 81mg ASA PO daily.
  • Consult heme/onc
  • Consider 3-5 million U interferon-α SQ daily if <40 years old. 15mg/kg hydroxyurea PO daily if >40 years old. Goal platelet count <400,000/microL.
  • Platelet apheresis if platelet count >800,000/microL.

Bleeding due to AT

  • Discontinue antiplatelet medications.
  • Consult.
  • Consider 3-5 million U interferon-α SQ daily if <40 years old. 15mg/kg hydroxyurea PO daily if >40 years old. Goal platelet count <400,000/microL.[5]

Disposition

Reactive thrombocytosis

  • Disposition is based on underlying disorder.

Autonomous thrombocytosis

  • If asymptomatic, consider outpatient treatment with close follow up.
  • If thrombosis or bleeding complications, should be admitted for stabilization and further work up.

External Links

References

  1. Schafer, "Thrombocytosis," N Engl J Med 2004;350:1211-9.
  2. Tefferi, "Diagnosis and Clinical Manifestations of Essential Thrombocythemia," UpToDate, Jul. 2017.
  3. Tefferi, "Diagnosis and Clinical Manifestations of Essential Thrombocythemia," UpToDate, Jul. 2017.
  4. uptodate
  5. Bleeker, "Thrombocytosis: Diagnostic Evaluation, Thrombotic Risk Stratification, and Risk-Based Management Strategies," Thrombosis. 2011; 2011: 536062. Published online 2011 Jun 8. doi:10.1155/2011/536062.