Polycythemia Vera (PV) is a rare blood disorder in which the number of red blood cells increases in the body. This increase of blood cell have many reasons, it could be due to a primary process in the bone marrow also known as Myeloproliferative Syndrome, or it may be due to low Oxygen levels or, rarely, a malignancy.

Polycythemia Poly is classified into two major groups.

• Polycythemia Vera - Primary Polycythemia
• Non Vera
    + Secondary Polycythemia
    + Relative Polycythemia

Primary Polycythemia (Polycythemia Vera)
In this type of Polycythemia excess red blood cells are produced, due to the abnormality of bone marrow. Often, excess white blood cells and platelets are also produced. Polycythemia Vera is classified as a myeloproliferative disease.

In Polycythemia Vera the blood become thicker and move slowly through the body, leading to less oxygen transport. This thick, slow-flowing blood can form clots, and it can lead to heart attack or stroke.

Secondary Polycythemia
When the production of erythrocytes is increased due to natural or artificial increases in the production of erythropoietin, Secondary Polycythemia is occurred.

There is another type of Secondary Polycythemia which is known as Physiologic Polycythemia. In this type of Polycythemia the production of erythropoietin increases appropriately. Physiologic Polycythemia are usually caused by oxygen deprivation: living in high altitudes, where oxygen availability is less than at sea level.

Relative Polycythemia
Relative poly is dehydration (low on plasma) which is caused by use of diuretics, drinking too little fluids etc.