For most people who have polycythemia vera (PV), there are no obvious reasons (risk factors) why they developed the disease. Most patients with PV don't have a family history of the disorder, although occasionally more than one family member has the disease.
PV occurs more often among Jews of Eastern European descent than among other Europeans or Asians. The average age at which PV is diagnosed is about 60 to 65 years. It is uncommon in individuals younger than 30 years.
How Does PV Develop?
PV results from a mutation (change) in a stem cell in the bone marrow, which leads to uncontrolled blood cell production, especially red cells. Because stem cells form red cells, white cells and platelets, any combination of these cell lines can be affected.
Blood cells function normally in patients with PV. Signs, symptoms and complications of PV occur because too many red cells and platelets are in the blood. Although PV may cause an increase in white cells, especially neutrophils, the excess white cells don't cause any significant adverse effects.
Although researchers don't fully understand what causes PV, almost all PV patients have a mutation of the JAK2 (Janus kinase 2) gene. This mutated gene likely plays a role in PV's onset. However, researchers are still studying its precise role as the cause of the disease.
Source: Polycythemia Vera. Reviewed by Srdan Verstovsek, MD, PhD.