Myelodysplastic syndromes (MDS)

What are myelodysplastic syndromes (MDS)?

Myelodysplastic syndromes (MDS) are a group of blood cancers that affect the blood and marrow. There are several types of MDS. Some progress slowly and may cause your body to produce a low number of red blood cells (anemia) or a decrease in white blood cells and/or platelets. Other types of MDS may cause more severe low blood cell counts. 

MDS may be primary, which has no obvious cause, or it may be related to earlier cancer treatment.

It's important that your doctor is experienced in treating patients with MDS or works in consultation with an MDS specialist. This type of specialist is called a hematologist-oncologist. Learn how to choose a blood cancer specialist or treatment center.

What should I do if I am diagnosed with MDS?

• Seek treatment in a cancer center where doctors are experienced treating patients with MDS.
• Talk with your doctor about your diagnostic tests and what the results mean.
• Ask your doctor whether a clinical trial is a good treatment option for you.

How does MDS develop?

 MDS starts with a change to a single stem cell in the bone marrow. This means:

• A normal stem cell mutates (changes) into an MDS cell (also called an “MDS blast cell”)
• The mutated cell multiplies into many MDS cells. These cells are often abnormal in shape and size. This condition is called “dysplasia.”
• The MDS cells build up in the bone marrow so there is less room for healthy blood cells to develop.
• The abnormal MDS cells do not grow into normal healthy blood cells, and they may die earlier than normal blood cells. As a result, people with MDS do not have enough healthy red blood cells, white blood cells and/or platelets.

Low blood cells can lead to the following conditions:

• Anemia: a condition where there is a low number of red cells in the blood, which can cause fatigue and shortness of breath
• Neutropenia: a condition where there is a low number of neutrophils (a type of white blood cell), so the immune system cannot effectively guard against infection.
• Thrombocytopenia: a condition where there is a low number of platelets, which can cause bleeding and easy bruising with no apparent cause
• Pancytopenia: a condition resulting from low numbers of all three blood cell counts

However, marrow cell disturbances in MDS patients range from mild to very severe. 

In some people, MDS cells can still function and enter the blood. Red cells continue to carry oxygen, white cells (neutrophils and monocytes) ingest and kill bacteria, and platelets plug up injury to blood vessels.

In more severe cases of MDS, blood cell formation is more disordered and abnormal blast cells (blasts) build up in marrow and blood. These cells don't mature into cells that function properly. They aren't as capable as normal cells are of maturing into red cells, neutrophils, and platelets.

Normally, blasts make up less than 5 percent of all cells in the bone marrow. With MDS, blasts often make up more than 5 percent of cells in marrow. The number of blasts is key to figuring out the severity of the disease.

What are risk factors for MDS?

Although in most cases it is not clear what causes the genetic changes in a blood cell that lead to MDS, there are some known risk factors. A “risk factor” is anything that increases a person’s chance of developing a disease.

The factors that are associated with an increased risk of developing MDS include:

• Age: risk increases with age
• Sex: males are more likely than females to develop MDS
• Genetic disorders: certain genetic conditions present at birth seem to increase risk
• Familial risk/germline predisposition
• Previous cancer treatment (referred to as "secondary" or "treatment-related MDS”)
• Smoking
• Workplace exposure to benzene among agricultural and industrial workers 

Find facts and statistics for MDS and other blood cancers.

Source: Myelodysplastic Syndromes. Reviewed by Guillermo Garcia-Manero, MD.