Polycythemia vera

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Clinical criteria

"Polycythemia vera is a clonal stem cell disorder characterized by excessive erythrocyte production. Its etiology is not fully established, but hypersensitivity to interleukin-3 may play a role in the sustained erythrocytosis observed in this disease.

Polycythemia vera usually occurs within the age range of 20-80, with 60 being the mean age of onset. The disease is slightly more common in males than in females. Clinical features include headaches, weakness, weight loss, and pruritus (itching without visible eruption on the skin). 10-15 % of patients may also present with gout due to hyperuricemia. Hemorrhage, thrombosis and hyperviscosity may be evident at any time. Splenomegaly, as a result of vascular congestion, is seen in 75% of patients at the time of presentation. Hepatomegaly is observed in about 30% of cases.

A diagnosis of polycythemia vera is made when a patent fulfills all three of the major criteria, or any two major and any two minor criteria.

  • Major Criteria
    • total RBC vol men > 36 mg/kg; women >32 mg/kg
    • arterial 02 saturation > 92%
    • Splenomegaly

=* Minor Criteria

    • Leukocytosis > 12 x 10^9/L
    • LAP > 100 (no infection)
    • Serum B12 > 900 pg/ml or UB12 BC> 2200 pg/ml [1]

JAK2 mutations

Mutations in the JAK2 gene, specifically at the V617F locus, give rise to myeloproliferative disorders such as essential thrombocythemia and polycythemia vera.[2]

Authors reported[3] that other mutations of the coding region of the JAK2 gene could create a polycythemia phenotype.

References

  1. Robert McLay and John Krause, Polycythemia vera, Tulane University
  2. Scott, et al. New Engl J Med 356: 459-468 2007.
  3. James, et al. Nature 434:1144-8 2005.