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N. Mariana S. Vasquez: JAK2 Mutations The High-Yield Map of Myeloproliferative Neoplasms
Sep 3, 2026, 17:24

N. Mariana S. Vasquez: JAK2 Mutations The High-Yield Map of Myeloproliferative Neoplasms

N. Mariana S. Vasquez, IMG Physician, shared a post on X:

“JAK2 Mutation: The High Yield Map Think myeloproliferative neoplasms when you see JAK2.

JAK2 V617F leads to constitutive JAK STAT signaling leads to increased myeloid proliferation

Polycythemia vera

  • JAK2 mutation leads to high RBC  production
  • high Hemoglobin or Hct
  • Low EPO
  • Pruritus after hot shower plus erythromelalgia

Essential thrombocythemia

  • JAK2 mutation leads to high megakaryocytes
  • Marked thrombocytosis
  • Thrombosis or bleeding

Primary myelofibrosis

  • JAK2 mutation leads to abnormal megakaryocytes
  • Cytokine release leads to bone marrow fibrosis
  • Massive splenomegaly plus teardrop RBCs
  • Extramedullary hematopoiesis

Important USMLE distinction

JAK2 is also seen in some MPNs without V617F, particularly JAK2 exon 12 mutations in polycythemia vera.

The classic MPN mutation pattern

PV leads to JAK2

ET leads to JAK2 or CALR or MPL

Primary myelofibrosis leads to JAK2 or CALR or MPL

Clinical shortcut

RBCs high plus EPO high leads to think PV leads to test JAK2

Platelets high leads to think ET leads to JAK2, CALR, or MPL

Massive spleen plus teardrop cells leads to think primary myelofibrosis.”

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