polycythemia vera

In oncology, polycythemia vera (PV) is an uncommon myeloproliferative neoplasm in which the bone marrow makes too many red blood cells. Approximately 98% of PV patients have a JAK2 gene mutation in their blood-forming cells (compared with 0.1-0.2% of the general population).

Most of the health concerns associated with PV, such as thrombosis, are caused by the blood being thicker as a result of the increased red blood cells.