Seema Dawood: What is Polycythemia Vera?
Seema Dawood, Medical Laboratory Technologist at The Aga Khan University Hospital, shared a post on Linkedin:
“Polycythemia Vera (PV)
Type of Myeloproliferative Neoplasm (MPN) characterized by an abnormal increase in red blood cell production in the bone marrow.
It is primarily caused by a JAK2 mutation (most commonly V617F), which makes hematopoietic cells overly sensitive to erythropoietin (EPO), leading to increased RBC production even when EPO levels are low.
Pathophysiology
- JAK2 V617F mutation is present in approximately 95% of cases.
- Another 2–3% carry JAK2 exon 12 mutations.
- The bone marrow becomes hypercellular with trilineage proliferation, involving erythroid, granulocytic, and megakaryocytic lineages.
- This results in elevated RBCs, WBCs, and platelets, a condition known as ‘Panmyelosis.’
Laboratory Findings
- Elevated Hb and Hct (Hct > 49% in men, > 48% in women)
- Increased RBC mass
- Low serum EPO (an important diagnostic clue)
- WBC and platelet counts may also be increased
- Bone Marrow
Hypercellular marrow
Trilineage growth: erythroid, granulocytic, and megakaryocytic proliferation
- Megakaryocytes are pleomorphic and often form clusters
- Genetics
Presence of JAK2 V617F or JAK2 exon 12 mutation
WHO Diagnostic Criteria (2022)
Diagnosis requires all 3 major criteria, or 2 major plus 1 minor.
- Major Criteria
Elevated Hb, Hct, or increased RBC mass
Bone marrow showing hypercellularity with Panmyelosis
JAK2 mutation (V617F or exon 12)
- Minor Criterion
Low serum EPO
- Complications
- Thrombosis
- Hemorrhage
- Splenomegaly
Disease progression to:
- Myelofibrosis (post-PV MF)
- Acute Myeloid Leukemia (AML) (less than 5%).”
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