What causes elevated platelet counts?

Causes of Elevated Platelet Counts

Elevated platelet counts (thrombocytosis) can result from various underlying conditions including iron deficiency, inflammatory diseases, infections, malignancies, and myeloproliferative disorders.

Primary vs. Secondary Thrombocytosis

Primary Thrombocytosis

• Myeloproliferative neoplasms - most common cause of primary thrombocytosis
  • Essential thrombocythemia
  • Polycythemia vera
  • Primary myelofibrosis
  • Chronic myelogenous leukemia

Secondary (Reactive) Thrombocytosis

• Iron deficiency anemia - common cause of reactive thrombocytosis 1, 2, 3

  • Iron therapy normalizes elevated platelet counts in patients with iron deficiency 3
  • May be related to elevated erythropoietin levels 4

• Inflammatory conditions

  • Inflammatory bowel disease 3
  • Rheumatoid arthritis
  • Connective tissue disorders
  • Vasculitis

• Infections - acute or chronic 2

• Post-surgical or post-traumatic states

• Tissue damage

  • Burns
  • Major trauma

• Post-splenectomy - due to lack of platelet sequestration 2

• Malignancies - solid tumors can cause paraneoplastic thrombocytosis

Diagnostic Approach

Laboratory Evaluation

• Complete blood count with peripheral smear
• Iron studies (ferritin, transferrin saturation) to rule out iron deficiency 3
• Inflammatory markers (CRP, ESR)
• Consider bone marrow examination if primary thrombocytosis is suspected

Mean Platelet Volume (MPV) Correlation

• High MPV with high platelet count: suggests myeloproliferative disorders, inflammation, iron deficiency, or post-splenectomy 2
• Normal MPV with high platelet count: suggests inflammation, infection, sickle cell anemia, iron deficiency, or chronic myelogenous leukemia 2

Clinical Significance and Management

Risk Assessment

• Primary thrombocytosis (especially with counts >1,000/μL) carries increased risk of thrombotic and bleeding complications 5, 6
• Secondary thrombocytosis, particularly with iron deficiency, may also increase thromboembolic risk 1

Management Principles

• Treat the underlying cause:

  • Iron supplementation for iron deficiency 3
  • Anti-inflammatory treatment for inflammatory conditions
  • Antimicrobials for infections

• For primary thrombocytosis:

  • Cytoreductive therapy with agents like anagrelide may be indicated 6
  • Starting dose of anagrelide: 0.5 mg four times daily or 1 mg twice daily 6
  • Goal: reduce platelet count below 600,000/μL, ideally between 150,000-400,000/μL 6

Special Considerations

• Platelet function may be more important than absolute count in determining bleeding risk
• Inflammation can alter platelet function through various mechanisms 7
• Secondary thrombocytosis was previously considered benign, but evidence suggests increased thrombotic risk, particularly with iron deficiency 1

Pitfalls to Avoid

• Assuming all cases of thrombocytosis are benign reactive processes without proper evaluation
• Overlooking iron deficiency as a cause of thrombocytosis
• Failing to assess for underlying malignancy in unexplained persistent thrombocytosis
• Not recognizing the potential thrombotic risk in secondary thrombocytosis, especially with iron deficiency