Myelofibrosis belongs to a group of rare diseases called myeloproliferative neoplasms, which are types of blood cancer. These neoplasms can progress to acute myeloid leukemia (AML).

In myeloproliferative neoplasms, a person’s bone marrow produces too many blast cells.

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.

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As the National Cancer Institute (NCI) describes, blast cells are immature and dysfunctional cells that develop 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 the following:

  • 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.
  • Chronic neutrophilic leukemia: The bone marrow produces too many neutrophils, which are a type of white blood cell.
  • Chronic eosinophilic leukemia: The bone marrow produces too many eosinophils, which are another type of white blood cell.

Myeloproliferative neoplasms can, in general, progress to AML. Doctors call this process blast-phase myeloproliferative neoplasm (MPN-BP).

According to a 2023 review, healthcare professionals define 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, according to a 2021 study. 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:

  • acute myeloid leukemia
  • acute lymphocytic leukemia
  • chronic myeloid leukemia
  • chronic lymphocytic leukemia

Two different factors distinguish these leukemia types:

  • Chronic versus 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 versus 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 acute form of leukemia in adults, accounting for close to 80% of leukemia 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, possibly 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:

  • monitoring the condition
  • chemotherapy
  • radiation therapy
  • stem cell transplant
  • targeted therapy, which uses medications or other substances to recognize and attack specific cancer cells
  • spleen removal
  • immunotherapy, which uses a person’s immune system to attack the cancer
  • phlebotomy, which involves a healthcare professional taking blood samples for testing in a laboratory
  • platelet apheresis, which involves separation of the platelets from whole blood
  • blood transfusion

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:

  • night sweats
  • fever
  • fatigue
  • unintentional weight loss
  • fullness or discomfort in the abdomen
  • quickly feeling full
  • pain while urinating
  • blood in the urine
  • gastrointestinal bleeding
  • pain in the bones

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

  • headaches
  • easy bruising
  • excessive bleeding
  • anemia, which may involve feelings of weakness and fatigue
  • frequent infections

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:

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.