Myelodysplastic syndromes are a complex group of blood disorders that affect how bone marrow produces healthy blood cells, leading to fatigue, infections, and bleeding problems. Understanding these conditions can help patients and families navigate the challenges ahead.

Understanding Myelodysplastic Syndromes

Myelodysplastic syndromes, often abbreviated as MDS and sometimes called myelodysplasia, represent a group of cancers that disrupt the normal functioning of bone marrow. The bone marrow is the spongy material inside bones where blood cells are made. In a healthy person, bone marrow creates immature cells called stem cells, which gradually mature into three types of fully functional blood cells: red blood cells that carry oxygen throughout the body, white blood cells that fight infections, and platelets that help blood clot to stop bleeding.^[1]

When someone has MDS, these stem cells either fail to mature properly or develop abnormally shaped cells. The immature blood cells, called blasts, do not work the way they should and may die in the bone marrow or shortly after entering the bloodstream. This leaves less room for healthy blood cells to form, resulting in lower counts of red blood cells, white blood cells, and platelets. Without enough healthy blood cells circulating in the body, a person may develop serious conditions including anemia (low red blood cell count), frequent infections due to low white blood cell count, and bleeding that won’t stop because of insufficient platelets.^[2]

The term myelodysplastic comes from Greek roots: “myelo” refers to marrow, and “dysplasia” means abnormal shape and appearance of cells. The word “syndromes” indicates a set of symptoms that occur together. MDS is considered a type of bone marrow failure disease, and in the past, it was sometimes called pre-leukemia. Now that more is understood about these conditions, they are classified as cancer. Approximately 30 percent of people with MDS may eventually develop acute myeloid leukemia (AML), a rapidly growing cancer of bone marrow cells.^[4]

How Common Are Myelodysplastic Syndromes

Myelodysplastic syndromes are relatively rare diseases. In the United States, approximately 4 in every 100,000 people are affected each year, with estimates suggesting that between 10,000 and 15,000 new cases occur annually. However, these numbers may underestimate the true prevalence because MDS can be difficult to diagnose and is not always reported consistently. The total number of people living with MDS in the United States is estimated to range from 60,000 to 170,000, though this wide range reflects differences in diagnostic practices and reporting methods across different populations.^[2][20]

MDS predominantly affects older adults, with the disease being diagnosed in people typically over the age of 65. The median age at diagnosis is approximately 70 years, and about 86 percent of patients with MDS are older than 60. The condition is uncommon before age 50, though it can occur in younger individuals. MDS does occur in children, but it is very rare, with only 1 to 4 cases per million children each year, and the median age of affected children is around 6.8 years.^[11][20]

The disease shows notable differences between genders and racial groups. Men are twice as likely to develop MDS as women, with the incidence ratio being approximately 4.5 cases in men for every 2 cases in women per 100,000 people. MDS is also more common in White individuals compared to other racial groups.^[11][20]

What Causes Myelodysplastic Syndromes

In most cases, the exact cause of myelodysplastic syndromes remains unknown. MDS is described as a clonal disorder of myeloid stem cells, meaning it originates from a single abnormal cell that multiplies uncontrollably. The condition may occur spontaneously without an identifiable cause, which is referred to as primary or de novo MDS. However, some cases can be traced to specific risk factors or exposures that damage the bone marrow.^[3]

One well-established cause is previous cancer treatment. MDS can develop as a secondary condition, also called treatment-related MDS, following chemotherapy or radiation therapy used to treat other cancers. These treatments, while effective against the original cancer, can damage healthy bone marrow cells and increase the risk of developing MDS later. Secondary MDS resulting from cancer treatment is actually more common than primary MDS that develops without a known cause.^[4]

Environmental and workplace exposures to certain chemicals have also been linked to MDS. Exposure to tobacco smoke, pesticides, and benzene increases the risk of developing the condition. Heavy metals such as mercury and lead may also contribute to MDS development. People who work in industries where they regularly encounter these substances may face higher risks.^[5]

Some individuals may have a genetic predisposition to developing MDS. Certain genetic conditions can increase susceptibility to the disease, suggesting that some people are born with a tendency to develop MDS if the right triggers are present. Changes or mutations in specific genes and chromosomes within bone marrow cells are commonly found in people with MDS. For example, many patients have deletions or losses of parts of chromosomes 5, 7, or 20, or they may have an extra copy of chromosome 8. Gene mutations in SF3B1 and TP53 are also frequently found in MDS cells.^[4]

Who Is at Risk for Developing MDS

Several factors increase the likelihood of developing myelodysplastic syndromes. Age is the single most significant risk factor. The vast majority of MDS cases occur in people over 65 years old, and the risk continues to increase with advancing age. This makes MDS primarily a disease of the elderly, though younger people can also be affected.^[3]

Individuals who have undergone chemotherapy or radiation therapy for another cancer face an elevated risk of developing MDS. The very treatments that successfully combat cancer can cause damage to bone marrow cells years later, leading to secondary MDS. This risk appears to be related to both the type and intensity of cancer treatment received.^[3]

Occupational exposures represent another important risk category. People who work with or are regularly exposed to certain chemicals, including benzene, pesticides, and other industrial compounds, have higher rates of MDS. Similarly, exposure to heavy metals like mercury or lead increases risk. Tobacco smoke exposure, whether through active smoking or significant secondhand smoke, also elevates the chances of developing the condition.^[5]

Certain inherited genetic conditions can predispose individuals to MDS. People born with these conditions carry a higher baseline risk throughout their lives. Gender also plays a role, with men being twice as likely as women to develop MDS. Additionally, being of White ethnicity is associated with higher MDS rates compared to other racial groups.^[11]

Signs and Symptoms

Many people with myelodysplastic syndromes do not experience noticeable signs or symptoms in the early stages of the disease. The condition often develops slowly over time, and symptoms may be mild at first, gradually worsening as blood cell counts continue to decline. Some people discover they have MDS only after routine blood tests reveal abnormal results. The symptoms that do develop depend largely on which type of blood cell is most affected.^[1]

Fatigue is one of the most common symptoms of MDS. This tiredness is not the ordinary fatigue that improves with rest. Instead, it is a persistent, overwhelming exhaustion that occurs because the body lacks sufficient red blood cells to carry oxygen to tissues and organs. People with MDS often describe feeling weak and lacking the energy to perform everyday activities. This fatigue can be accompanied by shortness of breath, especially during physical activity, and an unusual paleness of the skin called pallor. All these symptoms result from anemia, which affects the majority of people with MDS.^[1]

When white blood cell counts drop, frequent infections become a significant problem. White blood cells are the body’s primary defense against bacteria, viruses, and other harmful organisms. Without enough functioning white blood cells, even minor infections can become serious, and people with MDS may find themselves repeatedly falling ill. Fevers may occur frequently as the body attempts to fight these infections with limited immune resources.^[1]

Low platelet counts lead to bleeding and bruising problems. Platelets are essential for blood clotting, and when their numbers are insufficient, even small injuries can result in prolonged bleeding. People with MDS may bruise easily from minor bumps or notice that cuts and scrapes bleed longer than normal. Some individuals develop tiny red spots just beneath the skin called petechiae, which are caused by bleeding from small blood vessels. On lighter skin, petechiae appear as red or purplish dots, while on darker skin they may be brownish or difficult to see. These spots often appear on the legs, belly, or other parts of the body.^[1]

Other symptoms may include weight loss without trying, though this is less common in the early stages. Some people experience fever or night sweats. In certain cases where MDS overlaps with other bone marrow conditions, the spleen or liver may become enlarged, though this is not typical in most MDS cases.^[11]

Can Myelodysplastic Syndromes Be Prevented

Because the exact causes of most cases of myelodysplastic syndromes remain unknown, there is no guaranteed way to prevent the condition. However, reducing exposure to known risk factors may lower the chances of developing MDS, particularly secondary or treatment-related forms of the disease.^[5]

For individuals undergoing cancer treatment, prevention strategies are limited because chemotherapy and radiation are often necessary to treat life-threatening cancers. However, doctors carefully weigh the benefits of these treatments against potential long-term risks, including the possibility of developing MDS years later. When multiple treatment options exist, healthcare providers may consider choosing regimens with lower risks of causing future bone marrow problems, though this must always be balanced against the need to effectively treat the current cancer.^[3]

Avoiding or minimizing exposure to harmful chemicals offers another avenue for risk reduction. People who work in industries where they encounter benzene, pesticides, or other toxic substances should follow strict safety protocols, including using appropriate protective equipment and ensuring adequate ventilation. Reducing exposure to heavy metals like mercury and lead is also advisable. For the general population, avoiding tobacco smoke—both active smoking and secondhand smoke exposure—can reduce MDS risk along with many other health risks.^[5]

Regular medical checkups and blood tests can help identify blood cell abnormalities early, before symptoms develop. While this doesn’t prevent MDS, early detection may allow for earlier intervention and better management of the condition. People with risk factors such as previous cancer treatment, occupational chemical exposure, or advanced age should discuss with their doctor whether routine monitoring of blood counts is appropriate.^[1]

Maintaining overall health through a balanced diet, regular exercise, adequate sleep, and stress management supports the immune system and general well-being. While these measures cannot specifically prevent MDS, they contribute to better health resilience and may help the body better cope with various health challenges. For individuals with genetic conditions that increase MDS risk, genetic counseling may provide valuable information about monitoring strategies and what symptoms to watch for.^[16]

How MDS Affects the Body

Myelodysplastic syndromes fundamentally alter the normal process of blood cell production. In healthy bone marrow, stem cells undergo an orderly progression, dividing and maturing through several stages until they become fully functional red blood cells, white blood cells, or platelets. This carefully regulated process ensures that the body maintains appropriate numbers of each blood cell type to meet its ongoing needs. MDS disrupts this orderly system at its foundation.^[8]

The problem in MDS begins with the stem cells themselves. These early-stage cells carry genetic changes that prevent them from developing normally. Instead of maturing into healthy, functional blood cells, the stem cells produce abnormally shaped cells that don’t work properly. Many of these defective cells die within the bone marrow before they can even be released into the bloodstream. This process is called ineffective hematopoiesis—the bone marrow is actively producing cells, but the cells are dysfunctional and die prematurely, leading to a net decrease in healthy blood cells despite ongoing production.^[3]

The abnormal cells that do survive and enter the bloodstream cannot perform their intended functions effectively. Red blood cells may be unable to carry oxygen efficiently due to structural problems or insufficient hemoglobin, the oxygen-carrying protein. White blood cells may lack the ability to properly identify and destroy bacteria, viruses, and other pathogens, leaving the body vulnerable to infections. Platelets may be too small, oddly shaped, or lacking the necessary proteins to form blood clots effectively when bleeding occurs.^[2]

As immature blast cells accumulate in the bone marrow, they physically occupy space that would normally be available for healthy blood cell production. This crowding effect further reduces the bone marrow’s capacity to generate functional blood cells. The bone marrow may appear hypercellular—meaning it contains many cells—but these cells are predominantly dysfunctional blasts rather than healthy, mature blood cells. In about 10 percent of MDS cases, the bone marrow may appear hypocellular, meaning it contains fewer cells than normal, which also impairs blood cell production.^[11]

The accumulation of genetic changes in MDS cells can affect multiple aspects of cell function beyond just maturation. Changes in chromosomes—the structures that contain genes—are found in approximately 50 percent of people with MDS. These chromosomal abnormalities may include deletions where parts of chromosomes are lost, duplications where extra copies of chromosomes appear, or rearrangements where chromosome pieces break off and reattach in abnormal configurations. These genetic changes disrupt the normal signals that control cell growth, division, and death.^[11]

A particularly concerning feature of MDS is the potential for the disease to progress to acute myeloid leukemia. As genetic changes accumulate over time and blast cells increase in number, the line between MDS and AML can blur. By medical convention, when blast cells make up 20 percent or more of cells in the bone marrow or blood, the condition is reclassified as AML. This transformation occurs in roughly one-third of people with MDS, representing a significant change in disease characteristics and treatment approach.^[4]

Some MDS cells show a specific abnormality involving iron storage. Normally, developing red blood cells take up iron and incorporate it into hemoglobin. In certain types of MDS, immature red blood cells accumulate excessive iron in ring-like patterns around their nuclei, creating what pathologists call ring sideroblasts. This iron is trapped and cannot be used to make functional hemoglobin, contributing to anemia despite adequate body iron stores. The presence of ring sideroblasts helps doctors classify specific MDS subtypes.^[2]