Making sense of PV

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What are myeloproliferative neoplasms (MPNs)?

MPNs are a group of rare inherited conditions in which the body produces blood cells in an uncontrolled way. The name comes from ‘myelo’, which relates to the bone marrow and ‘proliferative’, which means ‘excess production’. Neoplasms are abnormal tissue masses.

There are three main types of MPN: essential thrombocythemia (ET), myelofibrosis (MF) and polycythemia vera (PV). These affect the blood cells in different ways.

MPNs are officially classified as blood cancers by the World Health Organization (WHO) since the bone marrow is producing blood cells in an uncontrolled way. However, PV usually develops slowly and those who do not suffer complications will usually have a normal or near-normal life expectancy.

+ What are the different types of blood cells?

Our bodies produce billions of blood cells every day. Production takes place in the bone marrow, the soft spongy tissue inside the bones. The bone marrow contains stem cells which are ‘master’ cells that divide and develop into the different types of blood cells the body needs.

There are three main types of cells, each of which plays a specific role:

  • Red blood cells contain a substance called hemoglobin, which carries oxygen to tissues in the body
  • White blood cells fight infection
  • Platelets control bleeding by helping blood to clot.

The body controls the production of blood cells to maintain the correct proportion of the different types of cells. When there is an imbalance in the numbers of different blood cells, this can lead to a range of disorders, including PV.

PV in brief

PV is a genetic condition associated with a mutation to a specific gene called JAK2 (Janus kinase 2). Over 95% of those affected by PV are estimated to have this mutation. Although it is caused by a genetic change, in fact it is rarely inherited.

People with PV produce more red blood cells than normal (this is called polycythemia), and also may produce too many platelets (thrombocythemia) and white blood cells (leucocytosis). When the blood contains too many blood cells, it can become thicker than normal and this can make it more difficult to flow freely through the arteries and veins. This can lead to a range of potentially serious health problems including blood clots (thrombosis), which can in turn lead to heart attacks and strokes. Additionally, when blood is thicker than normal, it moves more slowly and this can lead to low levels of oxygen in the blood, which can cause angina (chest pain) and heart failure.

About 75% of PV patients have an enlarged spleen (splenomegaly) or, less commonly, an enlarged liver (hepatomegaly). This is caused by a build-up of extra blood cells in the organ.

The goal of PV treatment is to manage symptoms and reduce the risk of complications.

PV is rare disease but knowledge about it is increasing all the time. A range of potential new treatments is currently being studied that have the potential to improve the outlook for people with PV as well as increasing quality of life.

+ Are there other names for PV?

Yes, there are a number of alterative names for PV.

It is also known as:

  • primary polycythemia
  • polycythemia rubra vera
  • erythremia
  • splenomegalic polycythemia
  • Vaquez’s Disease
  • Osler’s Disease
  • polycythemia with chronic cyanosis
  • myelopathic polycythemia
  • erythrocytosis megalosplenica, and
  • cryptogenic polycythemia

In the UK, the spelling is polycythaemia; US English spelling leaves out the "a". As a result, you will sometimes see the word spelled in slightly different way in different resources.

+ How many people are affected by PV?

PV is considered to be a rare disease – the number of people diagnosed each year is two to three per 100,000 people.

PV is more common in men than women. People over the age of 60 are more likely to be affected. There is a small number of cases in those under the age of 40.

+ Why do people get PV?

PV is related to a genetic mutation that occurs during adulthood. It is not something that people are born with. The cause of the mutation is unknown.

More than 95% of people with PV have a change (mutation) in a protein called JAK2 (JAK2V617F in full). This protein is part of the mechanism that controls how many blood cells the stem cells create.

Your guide to the symptoms of PV >

< PV: key facts