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What Are MPNs?

Myeloproliferative neoplasms (MPNs) is the name given to a group of conditions sometimes referred to as blood cancers. MPNs, previously known as myeloproliferative diseases (MPDs), are, in fact, stem cell disorders that develop when your body produces too many mature blood cells too quickly.

Why such a complicated name?

‘Myelo’ is the Greek word for marrow, ‘proliferative’ is another word
for ‘growing’ or ‘reproducing’ and ‘neoplasm’ means new growth.

The Spotlight on MPN website discusses three types of MPNs, the treatment and management options and the support that’s available for you. Also, you will be able to read stories from other people describing their experiences with these diseases.

Types of chronic myeloproliferative neoplasms

Myeloproliferative neoplasms are usually described depending on the type of blood cell that is most affected. There are four main types of MPNs that add up to approximately 95% of all cases:

This website discusses the three most common types of MPNs classified as ‘Philadelphia chromosome negative’ myeloproliferative neoplasms. Each affects a different type of blood cell and sometimes the body will make too many of more than one type of blood cell.

  1. Myelofibrosis (MF)
  2. Polycythaemia vera (PV)
  3. Essential thrombocythaemia (ET)



thrombocythemia (ET)

occurs when too many
platelets are made.

Myelofibrosis (MF)

is caused by an abnormality
in the cells that make platelets.
It results in bone marrow
being replaced by scar
(fibrous) tissue.

Polycythaemia vera (PV)

occurs when too many red blood cells are made.

Other types of myeloproliferative neoplasms include:
Chronic myeloid leukaemia (CML), Chronic neutrophilic leukaemia (CNL), chronic eosinophilic leukaemia (CEL) / hypereosinophilic syndrome, chronic myelomonocytic leukaemia (CMML), systemic mastocytosis.

It’s possible that you or your loved one might have features of more than one MPN when you’re first diagnosed. You might also have features of more than one during the course of the illness. In some cases, one disorder may transform to another.

What happens in the body?

In a healthy person, bone marrow makes blood stem cells that in time develop into mature blood cells – that is, red blood cells, white blood cells, or platelets.


Learn more about the role of
bone marrow and stem cells »

Each of these ‘mature’ blood cells is vital to maintaining your health because red blood cells carry oxygen and other materials to the tissues of your body, white blood cells fight infection and disease, and your platelets help prevent bleeding by causing blood clots to form.

MPNs develop when abnormal stem cells produce excess numbers of one or more of these blood cell types. Unable to function properly, they can trigger serious health problems unless properly treated and controlled.

It’s important to remember that myeloproliferative neoplasms are chronic diseases that, in most cases, remain stable for many years or may progress gradually over time. Many people with MPNs live normal lives for years at a time without experiencing complications.

Are they cancers?

Cancer is a disease that occurs when normal cells grow in an uncontrolled way. There has been some debate within medical circles about whether or not MPNs are types of cancer. This is because the word ‘neoplasm’ (new growth) is a term that doctors use both for cancers (malignant neoplasms) and non-cancerous tumours (benign neoplasms). The leading cancer organisations, such as the Leukaemia & Lymphoma Society in the US and Leukaemia & Lymphoma Research in the UK, consider MPNs to be cancers of the blood. The US government’s National Cancer Institute also describes MPNs as cancers.

An evolving area of medical research

Discovering MPNs – timeline of key dates

  • 1879: German surgeon Gustav Heuck writes about myeloproliferative disorders when he describes myelofibrosis.
  • 1892: French doctor Louis Hendri Vaquez writes about polycythaemia vera – the most common MPN.
  • 1903: American pathologist William Osler contributes more research on PV. (PV was for a time called ‘Vaquez Disease’ or ‘Osler-Vaquez Disease’.) Both men noted the reddening of the skin as a symptom and strokes as complications of the disease.
  • 1934: Austrian pathologists Emil Epstein and Alfred Goedel name essential thrombocythemia (ET) as a distinct clinical syndrome.
  • 1951: The three disorders are grouped together when eminent American haematologist William Dameshek (founder of the highly respected Blood journal) links them in his ground-breaking article ’Some Speculations on the Myeloproliferative Syndromes’.
  • 1960s: The Philadelphia (Ph) chromosome in CML is discovered, and science confirms CML is a clonal stem cell disease.
  • 1967: First large-scale clinical trials for polycythaemia vera (PV).
  • 1972: Janet Rowley discovered new relevance around the PH chromosome and how it worked.

In 2008, with the reclassification of the WHO diagnostic criteria, these diseases changed their name from myeloproliferative diseases to myeloproliferative neoplasms, implying and emphasising their definition as blood cancers.

– Professor Claire Harrison