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Diagnosis of Essential Thrombocythemia (ET)

Detection of ET is often made during routine CBC evaluation since symptoms may not initially appear. Symptoms, when they do occur, commonly include:
  • Thrombosis
  • Abnormal bleeding
  • Headaches
  • Tingling in the extremities
  • Pain in the extremities
Peripheral Blood Findings
The platelet count is greater than 600 x 109/L, frequently 1,000 - 5,000 x 109/L. Giant, bizarre platelets, platelet clumps, megakaryocytes or their fragments may be observed on the peripheral blood smear. Giant platelets are indicated by the arrows in the image on the right. Leukocytosis, erythrocytosis, or slight anemia may also be present. Since platelet counts are so high, the spleen can experience thrombotic episodes which eventually results in splenic atrophy. When this occurs, abnormal red cell morphologies such as red cell inclusions, nucleated red cells, and poikilocytosis, may be observed on the peripheral blood smear.

About half of patients diagnosed with ET have a JAK2(V617F) mutation. Other laboratory findings in ET include:
  • Normal or slightly increased thrombopoeitin
  • Usually normal prothrombin time (PT) and activated partial thromboplastin time (aPTT)
  • Platelet aggregation: abnormal with adenosine diphosphate, epinephrine, and collagen
  • Increased serum cobalamin, uric acid, LD, acid phosphatase
  • Philadelphia chromosome negative, BCR/ABL1 fusion gene negative