Polycythemia vera

• Erythroid proliferation predominates

• Usually in middle age and more in males

• Must be separated from relative (spurious) polycythemia from hemoconcentration and from secondary polycythemia from increased EPO secretion

  • This is best done by radiolabeling RBCs

  • In Lubbock, done by HCT

• Diagnostic criteria (diagnosis needs either all 3 major, or 2 major and 2 minor in the absence of splenomegaly)

  • Major

    • Absolute increase in RBC mass

    • Normal arterial O₂ saturation (rules out chronic hypoxia as a cause of erythrocytosis)

    • Splenomegaly (not seen in other causes of erythrocytosis…this comes from extramedullary hematopoiesis that’s going on the spleen because of the neoplastic stem cells that are there undergoing hematopoiesis)

  • Minor

    • Thrombocytosis

    • Leukocytosis (should see elevated neutrophils)

    • Elevated leukocyte alkaline phosphatase (LAP) score (this is how we can tell this apart from CML, which would have a decreased LAP score)

    • Elevated B₁₂ level or B₁₂ binding capacity (neutrophils are responsible for B₁₂ transport…if they are elevated, more B₁₂ can be bound)

• Clinical signs

  • Plethoric congestion of tissues from increased blood volume and viscosity

    • Vascular stasis and infarction common in heart, spleen, and kidneys

    • Intense pruritis (maybe form increased release of histamine by basophils; this may also cause the increased incidence of gastric ulcers)

    • Platelet dysfunction may lead to hemorrhage of GI tract or brain

    • H/A, dizziness, GI symptoms, hematemesis, and melena are common

    • High cell turnover leads to hyperuricemia (goes on to gout in 5-15%)

  • Hyperplastic bone marrow, but serum EPO low

    • Neoplastic stem cells have increased sensitivity to EPO and other growth factors

    • Disease progression may be seen as increasing marrow fibrosis or leukemic transformation

• Most patients are treated with therapeutic phlebotomy (leads to mean survival of 10 years); avoid chemo as long as possible (increases progression to AML to 15% [2% with phlebotomy])

• “spent phase”

  • Marrow been working hard and shuts down

  • Begin to see increased fibrosis and decreased cellularity in the marrow

  • May see an increase in splenomegaly from myeloid metaplasia trying to make up for failing marrow

  • Start to develop peripheral cytopenias

Category: Medical Subject Notes , Pathology Notes