What to do with thrombocytosis?

Management of Thrombocytosis with Platelet Count of 891k

For a platelet count of 891k (thrombocytosis), a comprehensive evaluation is necessary to determine the underlying cause, as this will guide appropriate management and reduce thrombotic or hemorrhagic complications.

Initial Assessment

• Determine if thrombocytosis is primary (clonal/essential) or secondary (reactive) 1, 2
• Evaluate for symptoms of thrombosis or bleeding 1
• Review complete medical history including:
  • Recent infections or inflammatory conditions 3
  • History of prior thrombosis 1
  • Recent surgeries or trauma 3
  • Iron deficiency 3, 2
  • Malignancy 2
  • Splenectomy status 2
  • Medications 3
  • Age (risk factor if >60 years) 1

Diagnostic Workup

• Complete blood count with peripheral smear to confirm true thrombocytosis 1
• Iron studies including ferritin (iron deficiency is a common cause of secondary thrombocytosis) 2
• Inflammatory markers (ESR, CRP) 3
• Consider JAK2, CALR, and MPL mutation testing if primary thrombocytosis is suspected 4, 2
• Bone marrow examination may be necessary if primary thrombocythemia is suspected 5

Risk Stratification for Essential Thrombocythemia

If primary thrombocythemia is diagnosed, risk stratification should be performed 6, 4:

• Very Low Risk: Age ≤60 years, no thrombosis history, JAK2 wild-type 4
• Low Risk: Age ≤60 years, no thrombosis history, JAK2 mutation present 4
• Intermediate Risk: Age >60 years, no thrombosis history, JAK2 mutation present 4
• High Risk: Any thrombosis history or age >60 years with JAK2 mutation 4

Management Recommendations

For Secondary Thrombocytosis (most common)

• Treat the underlying cause (infection, inflammation, iron deficiency, etc.) 3
• No specific treatment for the elevated platelet count is typically required 1, 3
• Monitor platelet count until resolution 3
• Secondary thrombocytosis rarely causes thrombotic complications, even with extreme elevation 1, 3

For Primary Thrombocythemia

Low-risk patients:

• Low-dose aspirin (81-100 mg daily) if platelet count <1,500 × 10^9/L 6, 4
• Observation without cytoreductive therapy is appropriate 6, 4

Intermediate-risk patients:

• Low-dose aspirin if platelet count <1,500 × 10^9/L 6, 4
• Consider cytoreductive therapy based on additional risk factors 6, 4
• Treat cardiovascular risk factors 6

High-risk patients:

• Cytoreductive therapy with hydroxyurea as first-line 6, 4
• Low-dose aspirin if platelet count <1,500 × 10^9/L 6, 4
• Alternative cytoreductive options include pegylated interferon-α or anagrelide 6, 4

Special Considerations

• Extreme thrombocytosis (>1,000 × 10^9/L): Consider cytoreductive therapy even in low-risk patients due to potential bleeding risk from acquired von Willebrand syndrome 6, 4
• Pregnancy: For high-risk pregnant patients, interferon-α is the preferred cytoreductive agent 6

Follow-up

• For secondary thrombocytosis: Monitor until resolution 3
• For primary thrombocythemia: Regular monitoring of platelet counts and assessment for complications 4
• Adjust therapy based on response and side effects 6, 4

Important Caveats

• Thrombocytosis is not always associated with increased thrombotic risk, especially in secondary cases 1, 3
• Extreme thrombocytosis (>1,500 × 10^9/L) may paradoxically increase bleeding risk due to acquired von Willebrand syndrome 6, 5
• Avoid heparin-based anticoagulants if there is concern for heparin-induced thrombocytopenia 1
• Secondary thrombocytosis in children is common and benign in most cases, rarely requiring treatment 1, 3