Myeloproliferative neoplasms (MPN)

Myeloproliferative neoplasms are a rare group of blood cancers. Polycythaemia vera is diagnosed in an estimated 250 Australians each year, essential thrombocythaemia around 200 and myelofibrosis an estimated 150. The rarer sub types of MPN, as a group, are diagnosed in less than 50 Australians per year.

Most people with an MPN have no family history.  MPN is more commonly diagnosed in people over the age of 50 although it can rarely occur in younger people, even very rarely in children.

The exact cause of MPNs remain unknown but there are likely to be a number of factors involved. That’s why MPNs, like most leukaemias and other cancers, become more common as we get older. A mutation of a particular gene (a segment of DNA that makes proteins) known as Janus kinase 2 (JAK2) is found in a large proportion of people with MPNs. The exact meaning of this mutation remains unclear but it appears to play a role in the overproduction of blood cells seen in these disorders. The discovery of a mutation in the JAK2 gene is important because it is likely to have a significant impact on the way MPNs are diagnosed and treated.

Long-term exposure to high levels of benzene or very high doses of ionising radiation may increase the risk of myelofibrosis in a small number of cases. Around one third of people with myelofibrosis have been previously diagnosed with polycythaemia or essential thrombocythaemia.

Many people have no symptoms when they are first diagnosed with an MPN and the disease is picked up accidentally during a routine blood test or physical examination. In other cases, people go to see their GP because they have some troubling symptoms of their disease. When symptoms do occur, they develop gradually over time. Common symptoms include:

• headaches
• blurred vision
• fatigue
• weakness
• dizziness
• itchiness (pruritus)
• night sweats
• raised blood pressure (hypertension).

Other symptoms experienced in MPN are a result of the affected cell involved with the MPN.

Enlargement of the spleen (splenomegaly) is common and occurs in around 75% of cases. In some cases the liver may also be enlarged: this is called hepatomegaly. Some people experience gout, which usually presents as a painful inflammation of the big toe or foot. Some individuals may develop erythromelalgia, a rare condition characterised by intense burning pain of affected extremities and an increased skin temperature. In many cases, people with PV have a ruddy (red) complexion, and a reddening of the palms of their hands, the soles of their feet, ear lobes, mucous membranes and their eyes. This is due to the high numbers of red cells in the circulation.

As the blood is thicker than normal it cannot flow as easily, especially through the smaller blood vessels. If left untreated, this increases the risk of the formation of a blood clot within a blood vessel. Blood clots are a common complication of PV and occur in around 30% of people, even before they are diagnosed. Bleeding and easy bruising can also occur. This is usually minor and occurs in around one quarter of all patients. Read more about PV here.

Similar to polycythaemia vera many people have no symptoms when they are first diagnosed with ET. Thrombosis (blood clot) is a major complication of ET. Blood clots can occur in large or small arteries, interfering with the blood and oxygen supply to various organs or tissues. Older patients and those with a high platelet count, or a prior history of thrombosis, may be at increased risk.

A major aim of treatment in ET is to reduce your platelet count, and therefore your risk of thrombosis. Less commonly, people experience symptoms of abnormal bleeding including bruising for no apparent reason, or exaggerated or prolonged bleeding following minor cuts or injury. In pregnancy, uncontrolled ET can reduce the blood supply to the placenta or fetus. This can cause problems with fetal growth and may in some cases lead to miscarriage. An enlarged spleen is common and occurs in around 30% of cases of ET. In some cases the liver may also be enlarged (hepatomegaly). Read more about ET here.

Virtually all patients with myelofibrosis have an enlarged spleen (splenomegaly) when they are first diagnosed, although around 20% of people will have no symptoms. In around a third of cases the spleen is very enlarged. Abdominal discomfort can also result from an enlarged liver (hepatomegaly), which occurs in around two-thirds of cases. Other less common symptoms include bone and joint pain, and bleeding problems.

Read more information about primary myelofibrosis here.

In the video below, MPN experts and people with lived MPN experience discuss some of the latest MPN treatment updates including:

Prof Andrew Perkins from Monash University.
Topic: Current clinical and research interests – rundown on how diagnosis and treatment is progressing and emerging therapies.

Prof Wendy Erber from University of Western Australia.
Topic: Why do Myeloproliferative Neoplasms Progress to Fibrosis?.

Prof Peter Baade from Cancer Council QLD.
Topic: How does the burden of MPN in Australia vary by where people live?

Helen Williams from Sydney. Helen is newly diagnosed with PV and discusses her experience from a patient perspective.