A 42-year-old woman is found incidentally to have a platelet count of 780,000/uL. She is asymptomatic, hemoglobin and total leukocyte count are normal, and the peripheral smear shows enlarged platelets without other abnormalities. JAK2 V617F mutation is detected. Splenomegaly is absent. What is the most likely diagnosis?

• A Reactive thrombocytosis due to iron deficiency
• B Essential thrombocythemia ✓
• C Polycythemia vera
• D Chronic myeloid leukemia

Explanation

Sustained thrombocytosis above 450,000/uL with isolated megakaryocytic proliferation, absence of significant granulocytic or erythroid expansion, and exclusion of reactive causes defines essential thrombocythemia; JAK2 V617F is present in roughly half of cases and supports clonality. Iron deficiency raises platelets reactively but lacks the JAK2 mutation, while polycythemia vera requires elevated red cell mass and CML requires BCR-ABL1.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.