Thrombocythemia

DDx of Thrombocythemia
Myeloproliferative disorder:
Chronic myelogenous leukemia: markedly increased WBC count, presence of a Philadelphia chromasome.
Myelofibrosis: abnormally shaped RBC (tear drops)
Polythemia vera
Essential (primary) thrombocytosis

Reactive thrombocytosis (usually platelets <1,000,000)
Inflammatory disease, e.g., rheumatoid arthritis, ulcerative colitis
Chronic infection
Iron-deficiency anemia
Postsplenectomy (transient)