What is Myelofibrosis?

Myelofibrosis is one of several types of blood cancer called “myeloproliferative neoplasms,” or MPN. The common factor in these diseases is that cells in the bone marrow that are supposed to mature into different kinds of blood cells (called stem cells) undergo mistakes in their genes that cause them to malfunction. Instead of multiplying and functioning normally, the irregular cells begin to grow without stopping, crowding out the normal blood cells that keep our bodies healthy. The different varieties of MPN depend on the type of cells that are affected.1

Myelofibrosis is a rare type of MPN in which abnormal blood cells and fibers grow too fast, causing scarring and damage to the normally spongy bone marrow.2

How does myelofibrosis develop?

Myelofibrosis begins when a stem cell in the bone marrow undergoes a mistake, or mutation, in its genes. Genes exist in every cell and serve as an instruction manual for the cell’s functioning and reproduction.3

When the mutated stem cell copies and divides itself, the mistake is passed onto the daughter cells, which themselves begin to divide and grow uncontrollably. These malformed blood cells, called “blasts,” stay immature and never develop properly. Over time, they crowd out the bone marrow’s ability to produce normal, healthy blood cells.2

The abnormal cells inside the bone marrow cause the normally spongy tissue to become scarred, or fibrous. Researchers believe that one reason for the scarring is the overproduction of a large, specialized cell called a megakaryocyte. Megakaryocytes are a type of white blood cell and a member of our body’s infection-fighting cells in our immune system. In myelofibrosis, too many abnormal megakaryocytes may overproduce chemicals called cytokines, which lead to inflammation and scarring.2

Many of the symptoms of myelofibrosis result from the inability of the bone marrow to produce normal, healthy blood cells.2,3 These include red blood cells, which carry oxygen through our body, white blood cells, which fight infection, and platelets, which cause our blood to clot.1

Risk factors for myelofibrosis

Myelofibrosis is a very rare disease. It’s exact cause is not known, but certain risk factors may increase your risk of developing the disease. These include:3

  • Age: Myelofibrosis can affect people at any age, but it is more common among people over 50.
  • Another blood cancer: A small number of people develop myelofibrosis as a side effect of a different type of blood cancer
  • Radiation exposure: Exposure to high levels of radiation has been linked to myelofibrosis.
  • Chemical exposure: Exposure to certain industrial chemicals such as toluene and benzene has been linked to myelofibrosis.

Symptoms of myelofibrosis

Myelofibrosis usually develops slowly and often does not cause symptoms in early stages. Many times it is diagnosed only from a routine blood test. Symptoms generally develop over time, as the mutated cells disrupt normal blood cell development. Common symptoms can include:3,4

  • Tiredness, weakness, shortness of breath, or pale skin, usually caused by low red blood cell numbers, also called anemia
  • More frequent illness or infections, usually caused by low white blood cell numbers, also called neutropenia
  • Easy bruising or bleeding, usually caused by low platelet numbers, also called thrombocytopenia
  • Enlarged liver (hepatomegaly)
  • Pain or fullness below the ribs on the left side, due to an enlarged spleen
  • Night sweats
  • Weight loss
  • Itchy skin
  • Fever
  • Bone or joint pain

What is a common prognosis for myelofibrosis?

A number of factors affect how effective treatment is likely to be when you have myelofibrosis. These take into account your overall health as well as various characteristics of your cancer.
People are grouped into low-, intermediate-, and high-risk groups. If you have low-risk myelofibrosis and are not experiencing symptoms, you might not need immediate treatment. People at high-risk, with more severe disease, may consider more aggressive treatments, including bone marrow transplantation.5
Doctors generally assess your individual prognosis by taking into account:6

  • Your age and overall health.
  • The number of abnormal red and white cells in your blood.
  • The number of abnormal blasts in your blood.
  • Whether you have particular mutations that researchers know to be related to your treatment outcome.
  • Whether you have symptoms such as fever, night sweats, or weight loss.

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