Myelodysplastic syndrome (MDS) is a rare group of blood cancers that causes the abnormal development of blood cells in the bone marrow.

In people with MDS, the bone marrow produces too many immature or defective blood cells that crowd out healthy white blood cells, red blood cells, and platelets.

In the past, myelodysplastic syndrome was referred to as “pre-leukemia” since MDS sometimes develops into acute myeloid leukemia. However, most people with MDS don’t develop leukemia, and this term isn’t commonly used anymore.

If you don’t have symptoms, your doctor may not recommend treatment right away and instead suggest regular monitoring to see whether the condition progresses.

Read on to learn why some people develop MDS and how it affects your body.

An estimated 20,541 people in the United States develop MDS each year. It’s still widely unknown what causes MDS, but it’s thought that genetic factors and exposure to certain chemicals could play a role.

When the cause isn’t known, it’s referred to as idiopathic or primary MDS. When environmental factors are suspected, it’s referred to as secondary MDS.

Genetic factors

Various genetic abnormalities may contribute to the development of MDS. More than 80 percent of people with MDS have changes in their genes, such as:

  • missing chromosomes
  • extra chromosomes
  • translocations, where a chromosome breaks and attaches itself to another chromosome

Researchers have also identified more than 100 gene mutations in people with MDS. Identifying these gene mutations can sometimes help doctors determine the person’s outlook. For example, a mutation in the gene TP53 is linked to a poorer outlook compared with other mutations.

MDS is usually not linked to family history, but some rare types do seem to be more common in families. MDS is more common in people with some syndromes that run in families, such as:

  • Diamond-Blackfan anemia
  • dyskeratosis congenita
  • familial platelet disorder with a propensity to myeloid malignancy
  • Fanconi anemia
  • severe congenital neutropenia
  • Shwachman-Diamond syndrome

Environmental factors and other risk factors

MDS is usually diagnosed in people ages 65 and older. It’s most common in people over 80.

Some chemotherapy drugs, such as alkylators and topoisomerase II inhibitors, can potentially contribute to the development of MDS 2 to 7 years after exposure. Only a small percentage of people who receive chemotherapy develop MDS.

The following also increases the risk of MDS:

  • combining chemotherapy with radiation therapy
  • receiving very large doses of chemotherapy, such as when undergoing a stem cell transplant
  • being exposed to high doses of radiation, such as a nuclear reactor or atomic bomb explosion survivors

People with long-term exposure to some chemicals like benzene may also have a higher chance of developing MDS. People at risk of benzene exposure include those who work in the petroleum, rubber, and agriculture industries.

According to the American Cancer Society, smoking cigarettes also increases your risk of developing MDS. Men are more likely to develop MDS than women, possibly due to a higher likelihood of smoking or exposure to workplace chemicals.

Studies have also shown an association between MDS and autoimmune disease. This is believed to be due to chronic inflammation driving the immune cells to replicate too frequently.

Many people with MDS don’t have symptoms in the early stages. In about 1 in 3 cases, it develops into acute myeloid leukemia over the course of months to years.

In people with MDS, the bone marrow produces new blood cells that are abnormal. They either don’t function properly or die quicker than they should and leave your body with a shortage of functional blood cells. A low blood cell count is called cytopenia, which is a prerequisite for an MDS diagnosis.

Your body has three types of blood cells:

  • Red blood cells carry oxygen from your lungs to other parts of your body.
  • White blood cells help protect your body from infections.
  • Platelets help your blood clot after an injury.

Your blood cells have a finite life. For example, red blood cells have an average life span of 120 days before your body breaks them down. Special cells in your bone marrow produce new blood cells to replace old or damaged ones.

People with MDS can develop a shortage of any type of blood cells. A shortage of red blood cells, called anemia, is most common. It causes symptoms such as:

Defective platelet levels can interfere with your blood’s clotting ability and cause symptoms such as easy or prolonged bleeding. Low white blood cells levels can weaken your immune system and make you more prone to infection.

The specific symptoms of MDS and its progression vary significantly between people. In the early stages, many people with MDS don’t have any symptoms or pain. But in many people, MDS and other blood cancers can cause bone or joint pain, often because bone marrow becomes overcrowded with cancer cells.

For example, about 25 percent of people with acute lymphoblastic leukemia have pain at the disease’s onset. Bone pain caused by MDS or leukemia is often described as a dull pain that continues even during rest. Some people experience sharp pain.

The most common place to experience bone pain is in the long bones in your arms or legs.

Bone pain is rarer with MDS and acute myeloid leukemia.

According to the American Cancer Society, a stem cell transplant is usually considered the only potential cure for MDS. Your doctor will assess whether the benefits of a stem cell transplant outweigh the risks, as they have too many risks for some patients.

If you’re not a good candidate for a stem cell transplant, your doctor may recommend other treatments to help you manage your symptoms and minimize your complications. Treatment options may include:

The survival rate for MDS varies depending on your overall health and many other factors. Even if your MDS can’t be cured, your doctor can recommend the best treatments and let you know about any clinical trials in your area you may qualify for.

Getting help

You can find many free support resources online, such as on the MDS Foundation website. Some of the resources they provide include:

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MDS is a group of cancers that causes abnormal development of blood cells. Many people with MDS don’t experience symptoms in the early stages.

MDS treatment as well as the outlook for people with MDS depend on many factors. Your doctor can help you determine whether treatment is needed, or if your condition can be managed with active surveillance.

If your doctor expects your MDS will progress very slowly, you might not need treatment at all. Many resources are available online to help you manage your MDS.