Types of MPN
What are the different types of MPN?
There are four main types of MPNs that together represent around 95 per cent of all cases:
- chronic myeloid leukaemia
- polycythaemia (rubra) vera (PV)
- essential thrombocythaemia (ET)
Less common types of myeloproliferative neoplasms include:
- chronic neutrophilic leukaemia (CNL)
- chronic eosinophilic leukaemia (CEL)/hypereosinophilic syndrome
- chronic myelomonocytic leukaemia (CMML)
- systemic mastocytosis
- myeloproliferative disease.
Polycythaemia (rubra) vera (PV)
The natural course of PV can vary considerably between individuals. In many patients, with treatment the disease remains stable for long periods of time, often many years. In around one third of all cases, PV transforms over time into another type of MPN called myelofibrosis, and in up to 10% of cases PV transforms into acute myeloid leukaemia.
In some people, PV progresses over time despite treatment. The spleen may become increasingly enlarged and in selected cases, surgical removal of the spleen or low dose radiation to the spleen may be required to relieve symptoms. Anaemia and thrombocytopenia (low numbers of circulating platelets) is common as the bone marrow is no longer able to produce adequate numbers of red cells or platelets. In addition, abnormal immature blood cells known as blast cells may start to appear in the blood.
Treatment during this time may involve blood transfusions if required, pain relief and careful myelosuppression. Your doctor is the best person to give you an accurate prognosis regarding your disease as he or she has all the necessary information to make this assessment.
Essential thrombocythaemia (ET)
ET is regarded as an incurable disease but in many people, with treatment the disease remains stable for long periods of time, often 10-20 years or more. In the longer term, a small number of people with ET may develop myelofibrosis. The risk of ET transforming to acute myeloid leukaemia is relatively low (1-2%).
Myelofibrosis (also called chronic myelofibrosis, agnogenic myeloid metaplasia).
Myelofibrosis is generally regarded as an incurable disease but with treatment many people can remain comfortable and symptom-free for some time. The natural course of the disease can vary considerably between individuals. In some people their disease remains stable for long periods and they are free to live a normal life with minimal interruptions from their disease or its treatment. For others, myelofibrosis progresses more quickly and people require treatment to help relieve symptoms of their disease. Transformation into acute myeloid leukaemia occurs in between 10% and 20% of cases.
Chronic neutrophilic leukaemia (CNL)
Chronic eosinophilic leukaemia (CEL)/hypereosinophilic syndrome
CEL is a rare disease and its natural course can vary considerably between individuals. The disease may remain stable for many years, even decades, or it may quickly progress and transform to acute leukaemia. For this reason, the most appropriate treatment for each patient is decided on an individual basis.
Treatment may include corticosteroids, chemotherapy drugs such as hydroxyurea, and interferon therapy. Some patients may respond to a newer drug called imatinib mesylate (Glivec), most often used in the treatment of another type of MPN called chronic myeloid leukaemia. A stem cell transplant may be considered in selected cases.
Systemic mastocytosis or mast cell disease
Medications known as antihistamines are used to prevent and reduce allergic reactions. Treatment decisions tend to be made on an individual basis and may include chemotherapy in tablet form and/or interferon to help control the overproduction of mast cells in the bone marrow. Research indicates that new tyrosine kinase inhibitors may also be useful as a treatment therapy.