Myelofibrosis belongs to a group of rare diseases called myeloproliferative neoplasms, which are types of blood cancer in which a person’s bone marrow produces too many blast cells. Myeloproliferative neoplasms have the capacity to progress to acute myeloid leukemia (AML).

Myelofibrosis, also known as primary myelofibrosis, is the most common type of myeloproliferative neoplasm to progress to AML.

This article explains what experts know about the progression of myelofibrosis to AML. It also gives an overview of both conditions, including their treatment options and the outlook for people living with them.

Middle-aged doctor or scientist examining cells through microscopeShare on Pinterest
RUNSTUDIO/Getty Images

As the National Cancer Institute (NCI) describes, blast cells are immature and dysfunctional cells that develop very quickly and crowd out healthy blood cells in the bone marrow. Blasts can be red blood cells, white blood cells, or platelets. Depending on the type of cell involved and the stage of disease, these conditions, known as myeloproliferative neoplasms, can lead to anemia, fatigue, or infection, among other symptoms.

The name of the myeloproliferative disorder is based on the type of cell involved. According to the NCI, myeloproliferative neoplasms include:

  • Myelofibrosis: The bone marrow forms abnormal blood cells and fibrous tissues.
  • Chronic myeloid leukemia: The bone marrow produces too many white blood cells.
  • Polycythemia vera: The bone marrow produces too many red blood cells.
  • Essential thrombocythemia: The bone marrow forms too many platelets.

Myeloproliferative neoplasms can, in general, progress to AML. As a 2021 review outlines, this process is called blast phase myeloproliferative neoplasm (MPN-BP). The World Health Organization (WHO) defines MPN-BP as any myeloproliferative neoplasm alongside which blast cells represent at least 20% of the cells in the blood or bone marrow.

AML will occur in about 5–10% of people with a myeloproliferative neoplasm. This progression is most common in people with myelofibrosis. Within a 10-year period, approximately 20% of people with myelofibrosis will develop AML.

Myelofibrosis vs. polycythemia vera diagnosis

Myelofibrosis is just one type of myeloproliferative neoplasm that can progress to AML. Doctors must distinguish it from a condition called polycythemia vera, which myelofibrosis can often resemble. However, only 4% of those with polycythemia vera will develop AML.

Leukemia is the umbrella term for blood cancers involving the white blood cells. There are four main types of leukemia:

Two different factors distinguish these leukemia types:

  • Chronic vs. acute leukemia: With acute leukemia, the bone marrow produces too many abnormal white blood cells. These are either myeloid blasts or lymphoid blasts. These cells multiply quickly and crowd out healthy bone marrow cells. In contrast, the bone marrow of a person with chronic leukemia produces too many mature and functional cells.
  • Myeloid vs. lymphocytic leukemia: Myeloid leukemia involves myeloid cells, such as monocytes, neutrophils, and macrophages. Lymphocytic leukemia affects lymphoid cells, such as T cells and B cells.

AML is the most common form of leukemia, accounting for close to 80% of cases.

The NCI explains that there is no general staging system for the progression of myeloproliferative neoplasms, as experts do not know exactly how myelofibrosis progresses into AML. The reason for this is that many different kinds of genetic mutations seem to be involved in the transformation process, which can itself vary depending on which genetic mutations are the first to develop.

Most myeloproliferative neoplasms progress to AML gradually, perhaps over the course of several years. However, the progression can be much quicker for some people. One sign of progression is a higher percentage of blast cells, meaning at least 20%, in the bone marrow and blood. Frequent medical visits are necessary to monitor the percentage of blast cells.

Factors associated with progression

Knowing the likely outcome of myelofibrosis helps determine the most appropriate type and timing of treatment. Healthcare professionals use specific scoring systems for estimating a person’s outlook. According to the myelofibrosis treatment algorithm, known as the Dynamic International Prognostic Scoring System (DIPSS), factors associated with a less positive outlook include:

  • being 65 years of age or older
  • having less than 10 grams of hemoglobin per deciliter of blood
  • having more than 25,000 white blood cells per microliter of blood
  • blast cells representing at least 1% of the cells in circulation (peripheral blood, not bone marrow)
  • the presence of fatigue, anemia, or other signs and symptoms of myelofibrosis

DIPSS-independent risk factors include the presence of specific genetic changes in the myeloid blast cells, the person’s need for red blood cell transfusion, and low platelet count.

Many different treatment options can help reduce the chances of myelofibrosis progressing to leukemia. The NCI lists the following:

As with any form of treatment, the most appropriate option will depend on the individual. A 2019 study notes that certain drugs, such as danazol and drugs that stimulate red blood cell production, could worsen someone’s myelofibrosis, making the development of AML more likely.

If someone has myelofibrosis without AML, their outlook will largely depend on the severity of any symptoms they are experiencing. The symptoms of myelofibrosis include:

Should myelofibrosis progress to AML, a person may also experience some common AML symptoms, including:

Although doctors can cure AML in about 40% of people younger than 60 years, the cure rate is 15% in older people. The reasons for this difference may include:

Learn more about medications and other treatments for AML.

Myelofibrosis can progress to AML, which is a very severe condition, through a complex process of genetic mutation. Some treatments can reduce the chances of myelofibrosis progressing to AML.

Several factors will determine the outlook of people with these conditions, including age, symptom severity, and the effectiveness of treatment.