Thrombocytosis, Thrombocytopenia, and Thrombocytopathy
Classification, Etiology, Pathogenesis, and Clinical Manifestations
Thrombocytosis: Increased platelet count >450,000/ μL.
Thrombocytopenia: Decreased platelet count <150,000/ μL.
Thrombocytopathy: Normal platelet count but abnormal function.
Classification
Thrombocytosis
Thrombocytopenia
Thrombocytopathy
Etiology
- Thrombocytosis:
- Primary: JAK2 mutations (e.g., essential thrombocythemia).
- Secondary: Infection, inflammation (IL-6 → thrombopoietin), trauma, cancer, post- splenectomy.
- Thrombocytopenia:
- Bone marrow failure, hematologic malignancies.
- Autoimmune destruction: ITP, SLE.
- Drug-induced: Heparin (HIT), quinine.
- DIC, TTP, HUS.
- Thrombocytopathy:
- Inherited: platelet receptor defects.
- Acquired: Uremia, liver disease, drugs inhibiting platelet aggregation.
Pathogenesis
- Thrombocytosis
- Primary: Clonal expansion of megakaryocytes in bone marrow → uncontrolled platelet production.
- Secondary: Inflammation or malignancy ↑ IL-6 → ↑ thrombopoietin → ↑ platelet synthesis.
- Possible complication: thrombosis (especially in primary forms).
- Thrombocytopenia
- ↓ Production: Bone marrow suppression or infiltration → ↓ megakaryocyte activity.
- ↑ Destruction: Immune system targets platelets (e.g., ITP) or consumption in DIC.
- Sequestration: Enlarged spleen holds excess platelets → functional shortage.
- Possible complication: bleeding risk, especially when <50,000/ μL.
- Thrombocytopathy
Platelets are present in normal numbers but have:
- Defective adhesion (e.g., GPIb defect).
- Defective aggregation (e.g., GPIIb/ IIIa defect).
- Impaired secretion of granule contents.
- Result: Ineffective platelet plug formation → mucocutaneous bleeding.