Myelofibrosis: Facts and Statistics: What You Need to Know

Myelofibrosis is a rare bone marrow disease that occurs when the bone marrow becomes fibrotic (filled with scar tissue). It leads to an enlarged spleen, leukopenia (low white blood cells), anemia (low numbers of healthy red blood cells), and thrombocytopenia (low platelets). These effects are harmful, and they can be life-threatening.

The incidence of newly diagnosed myelofibrosis cases in the United States is approximately 1 to 3 per 100,000 people per year. About 8% to 30% of people diagnosed with myelofibrosis eventually develop acute myeloid leukemia, a serious type of bone marrow cancer.

This article will discuss facts and statistics for myelofibrosis, including how rare it is, who it affects, causes, treatment, and mortality rates.

Myelofibrosis Overview 

In myelofibrosis, the bone marrow, which normally produces blood cells, is filled with scar tissue. Fibrotic bone marrow no longer adequately produces blood cells. The effects of myelofibrosis can range from mild (almost no symptoms) to severe (life-threatening).

Consequences of the condition can include:

• A lack of platelets leads to bruising and bleeding, which can cause severe blood loss.
• A deficiency of white blood cells leads to infections and cancer risk.
• A low number of red blood cells causes anemia and comes with symptoms of fatigue and low oxygen.

The spleen (an organ in the abdomen where blood cells get recycled) can become enlarged and may rupture. Portal hypertension (a condition of the liver's blood vessels) can lead to liver failure.

How Common Is Myelofibrosis? 

Myelofibrosis is diagnosed in approximately 1 to 3 out of 100,000 people in the United States per year, and it’s estimated to affect approximately 1 out of 200,000 people in Northern Europe.

The worldwide incidence and distribution of the disease in most countries is not known. This is because diagnosis, testing, and treatment have improved over the last 20 years, and the data are just now emerging.

According to one large study, there may be an increased genetic risk among people who are New Zealand Polynesians. Another study, performed in Sweden, observed that documented cases of myelofibrosis are increasing, but the authors suggest that this could be due to enhanced diagnosis.

Myelofibrosis by Ethnicity

According to the preliminary findings from a large Chinese study, the reliability of tests used to determine the prognosis of myelofibrosis may differ for ethnic or regional populations. 

Additionally, a bone marrow transplant is one of the treatments, and the availability of matched donors for bone marrow transplant differs among ethnic populations.

Myelofibrosis by Age and Gender 

Most U.S. studies suggest that the incidence of primary myelofibrosis is equal for adults of any sex.

The average age of diagnosis is 64, and the condition typically develops after age 50. It can occur at any age, however.

Children can get myelofibrosis, although it is extremely rare. When they do, it’s usually diagnosed before age 3. Female children are more likely to develop myelofibrosis during childhood than male children. 

Causes of Myelofibrosis and Risk Factors

Myelofibrosis is characterized as either primary or secondary. Secondary myelofibrosis develops due to another disease. Primary myelofibrosis is considered idiopathic—without a known predisposing cause.

Primary Myelofibrosis

The primary form of the disease usually occurs due to certain genetic mutations (changes in a person’s DNA). The mutation usually occurs without being inherited.

Associated genetic changes are identified in about 90% of primary myelofibrosis, and a mutation of the JAK2 gene accounts for approximately half of the cases of primary myelofibrosis. This gene guides the rate of blood cell production.

Factors associated with primary myelofibrosis occurrence include:

• Smoking 
• Toxin exposure 
• Obesity
• Autoimmune or inflammatory disease

Secondary Myelofibrosis

Secondary myelofibrosis is a complication of bone marrow disease, bone marrow cancer, or cancer treatment that suppresses the bone marrow. It develops when the bone marrow is damaged, which can cause fibrosis. 

Conditions that can lead to secondary myelofibrosis include:

• Polycythemia vera: A disorder in which the bone marrow makes too many blood cells
• Multiple myeloma: A rare type of blood cancer involving immune-system cells called plasma cells
• Leukemia: Cancers of the white blood cells
• Lymphoma: Cancers of lymphatic system cells
• Radiation exposure
• Metastatic cancer: Cancer that has spread from its origin to other tissues and organs

What Are the Mortality Rates for Myelofibrosis? 

Myelofibrosis leads to complications that can be fatal, including hemorrhage (bleeding) and thrombosis (blood clots in an artery or vein). Progression to cancer can also increase the risk of death. 

The estimated 10-year survival rate is 55%. This rate is an improvement that has taken place since the Food and Drug Administration (FDA) approval of Jakafi (ruxolitinib), a Janus kinase (JAK) inhibitor. Other JAK inhibitors approved for treating myelofibrosis include Inrebic (fedratinib) and Vonjo (pacritinib).

Various systems are used in prognosis, which is predicting an individual's estimated survival with myelofibrosis. 

The commonly used scoring systems include:

• Genetically inspired prognostic scoring system (GIPSS): Uses the type of mutation to estimate disease outcome
• Mutation- and karyotype-enhanced international prognostic scoring system (MIPSS): Estimates prognosis using the type of mutation, combined with risk factors

These scoring systems may be used to help decide on the best options for treatment.

Screening and Early Detection 

If you are at risk of secondary myelofibrosis due to a history of cancer treatment or bone marrow disease, you will likely have scheduled blood tests to identify changes in your blood cells.

If you have signs or symptoms of the condition, testing will include blood tests, imaging, and possibly a bone marrow biopsy to help determine whether you have myelofibrosis. In a bone marrow biopsy, a sample is taken from a bone (usually the hip) and analyzed in the lab.

If you are diagnosed with myelofibrosis, you may have genetic testing to identify mutations as part of your diagnostic process. 

Summary

Myelofibrosis is a rare bone marrow disease. The condition causes changes in blood cell production, and this leads to many medical complications. Myelofibrosis can be associated with previous bone marrow cancer, and it can also lead to bone marrow cancer.

Primary myelofibrosis occurs due to changes in genes that are usually not inherited. Secondary myelofibrosis occurs as a complication of bone marrow disease or as a side effect of bone marrow suppression treatment. Survival is improving with new therapies, including JAK inhibitors and bone marrow transplant.