Polycythemia vera rubra (increased blood cells)

General or Other | Hematology | Polycythemia vera rubra (increased blood cells) (Disease)


Description

Polycythaemia rubra vera (PRV) is not simply a high haemoglobin value but a myeloproliferative disorder. There is not only excessive production of normal erythrocytes but also increased production of leucocytes and platelets.

In PRV, a single clone of erythrocytes, granulocytes, B cells, and platelets arises when a haematopoietic stem cell gains proliferative advantage over other stem cells. T lymphocytes and natural killer cells remain polyclonal. This can be tested only in female patients as it uses polymorphisms on the X-chromosome and takes advantage of its inactivation. The red cells have normal responsiveness to erythropoietin but they are not dependent upon it to multiply.

Causes and Risk factors

There is a risk of transformation to acute myeloid leukaemia. Genetic studies suggest that the appearance of the abnormal stem cells in a person with PV is due to a mutation in a gene or genes in a single cell. The trigger for this is not understood, but as in cancer and leukemia, agents like radiation or toxic chemicals (eg benzene) may be suspected in some cases.

For most of us it is not possible to track down a specific cause. The criteria that must be met for a diagnosis of PV, and the incidence of these abnormalities at diagnosis, are: an increased red cell mass and an enlarged spleen (splenomegaly, which is present in 75% of cases), or any two other features of pluripotential precursor cell involvement, such as increased platelet counts (35-50%), neutrophilia (50-80%), increased leukocyte alkaline phosphate activity (80%), or increased vitamin B12 binding protein (67%).

Diagnosis and Treatment

The goal of treatment is to reduce the thickness of the blood and prevent bleeding and clotting.

A method called phlebotomy is used to decrease blood thickness. One unit of blood (about 1 pint) is removed weekly until the hematocrit level is less than 45 (males) or 42 (females). Then therapy is continued as needed.

Occasionally, chemotherapy (specifically hydroxyurea) may be given to reduce the number of red blood cells made by the bone marrow. Interferon may also be given to lower blood counts. A medicine called anagrelide may be given to lower platelet counts.

Some patients are advised to take aspirin to reduce the risk of blood clots, though it increases the risk for stomach bleeding. Ultraviolet-B light therapy can reduce the severe itching some patients experience.

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