Final answer:
Polycythemia vera (PV) is a bone marrow disease characterized by the excessive production of red blood cells, leading to an elevated hematocrit and increased blood viscosity. It is a rare condition that occurs more frequently in men and elderly patients.
Step-by-step explanation:
Polycythemia vera (PV) is a primary absolute disorder characterized by the excessive production of red blood cells. It is a bone marrow disease that causes an abnormal increase in the number of immature red blood cells. This condition can lead to an elevated hematocrit and increased blood viscosity, making it more difficult for the heart to pump blood throughout the body. PV is a relatively rare disease that occurs more often in men than women and is more likely to be present in elderly patients.