Myelofibrosis (pronounced MY-eh-loh-fy-BROH-sis) is a hematologic (blood) cancer that falls into the category of myeloproliferative neoplasms (MPNs). MPNs are a group of cancers that affect the bone marrow. Understanding more about this rare diagnosis, its potential treatments and the types of support available to you is key. The more you know and understand, the more prepared you will be to make important decisions in the future.

Following are the three main types of MPNs and the defining characteristic of each.

  • Essential thrombocythemia (ET) — too many platelets are produced.
  • Polycythemia vera (PV) — too many red blood cells are produced.
  • Primary myelofibrosis — too many fibroblasts, which are connective tissue cells that make and secrete collagen proteins, are produced.

The Basics of Myelofibrosis

It’s important to know how cancer develops and how it impacts bone marrow. Normally, cells divide in an orderly fashion. When they are worn out or damaged, they die, and new cells replace them. Cancer develops when genes within normal cells begin to change, or mutate. These cells – now called cancer cells – grow and displace normal cells.

Bone marrow is the soft, spongy center of some bones. It is where blood is created and is made up of blood stem cells, more mature blood-forming cells, fat cells and supporting tissues. Blood stem cells can become:

  • Red blood cells, which carry oxygen from the lungs to other parts of the body
  • White blood cells, which fight off infection and other foreign intruders in the body
  • Platelets, which help with clotting to stop bleeding

Myelofibrosis starts in the bone marrow when abnormal blood stem cells produce immature cells that grow quickly and take over. The immature cells become fibrous and fill the bone marrow with scar tissue. As a result, not enough normal blood cells can be made, and other organs, such as the spleen or liver, may try to compensate and become enlarged in the process.

You may have some symptoms of the disease at diagnosis, and others may develop. These may include weight loss, feeling full quickly, fever, night sweats, fatigue, itching (especially after bathing), bone pain and abdominal discomfort or bloating. Your doctor will ask at each follow-up visit if you’re experiencing any of these symptoms. It is also important to let your doctor know if they occur between visits.

When myelofibrosis develops spontaneously, it is known as primary myelofibrosis. It can also arise from other bone marrow diseases. Both ET and PV can progress to myelofibrosis. When myelofibrosis develops from other blood disorders, including ET or PV, it is known as secondary myelofibrosis. Although myelofibrosis is considered a chronic blood cancer, in some cases it can transform to acute myeloid leukemia.

This content focuses on primary myelofibrosis and its diagnosis, treatment and side effects.

Diagnosing and Classifying Myelofibrosis

Each person’s disease develops differently with a variety of symptoms, which is why diagnosing myelofibrosis can take some time. Multiple tests are used to diagnose it, and other types of blood and bone marrow cancer that have similar features must be ruled out. Testing typically includes a physical exam, a symptom survey, blood tests, a bone marrow biopsy, and chromosome and specific gene testing, among others (see Genetic Testing). Imaging studies to evaluate the size of the liver and spleen are also commonly included in the initial evaluation.

Once the diagnosis is confirmed, your doctor will use a prognostic scoring system that determines your prognosis (outcome) based on risk factors. This helps your doctor develop a personalized treatment strategy for you.

The Dynamic International Prognostic Scoring System (DIPSS) Plus, which scores risk during treatment, is commonly used. It divides risk into four tiers: low risk, intermediate-1 risk, intermediate-2 risk and high risk. You will be treated based on your risk score and other factors (see Treatment Options). Multiple prognostic scoring systems exist. If you are unsure which one your doctor used, ask.