Myelodysplastic syndrome transformation refers to the progression of myelodysplastic syndromes into acute myeloid leukemia, a serious complication that affects approximately one-third of people living with this group of blood disorders. Understanding this transformation process, its warning signs, and risk factors can help patients and their families prepare for what lies ahead and make informed decisions about their care.

Understanding Myelodysplastic Syndromes and Their Nature

Myelodysplastic syndromes, often shortened to MDS, represent a diverse collection of blood disorders that develop in the bone marrow, the soft tissue inside your bones where blood cells are made. In MDS, the bone marrow, which normally acts like a factory producing healthy blood cells, starts to produce cells that don’t develop properly or function as they should. These abnormal cells either die in the bone marrow or shortly after entering the bloodstream, leaving the body without enough healthy red blood cells, white blood cells, or platelets.^[1]

The condition is classified as a clonal disorder, meaning it begins when a single stem cell develops genetic changes and then multiplies uncontrollably, creating many copies of itself with the same defects. These defective cells gradually crowd out the healthy cells in the bone marrow. What makes MDS particularly concerning is its nature as a “premalignant” condition – while it isn’t cancer in the traditional sense at diagnosis, it has the potential to become more aggressive over time.^[5]

What Is Myelodysplastic Syndrome Transformation?

Transformation refers to the progression of MDS into acute myeloid leukemia (AML), a type of blood cancer. This happens when the percentage of immature blood cells called blasts increases significantly in the bone marrow or bloodstream. In medical terms, when blast cells reach or exceed 20 percent in the blood or bone marrow, doctors reclassify the condition from MDS to AML.^[9]

Not everyone with MDS will experience this transformation. Research indicates that only about one-third of people diagnosed with MDS will actually progress to leukemia. For the remaining two-thirds, the condition may remain stable for years, or patients may experience complications related to low blood cell counts without ever developing leukemia.^[2]

When transformation does occur, it represents a significant change in the disease’s behavior. The leukemia that develops from MDS tends to be more difficult to treat than leukemia that develops on its own, without a prior history of MDS. This is because the cells have already undergone multiple genetic changes, making them more resistant to standard chemotherapy treatments.^[1]

How Common Is This Transformation?

Myelodysplastic syndromes themselves are relatively uncommon conditions. In the United States, slightly more than 10,000 people are diagnosed with MDS each year, with an annual rate of approximately 4.4 to 4.6 cases per 100,000 people. The condition is more frequently seen in men than women and appears more commonly in White individuals.^[9]

MDS predominantly affects older adults, with most people diagnosed after age 60. The median age at diagnosis is approximately 70 years, though the condition can occur at any age, including in children, though this is extremely rare. In children, MDS occurs in only about four out of every one million, making it exceptionally uncommon in younger populations.^[2]

What Causes MDS and Its Transformation?

The root cause of MDS lies in damage to the genetic material of blood-forming stem cells in the bone marrow. In about 90 percent of cases, MDS develops without any identifiable cause – doctors call this “de novo” MDS, meaning it arises spontaneously. However, various factors can increase the risk of developing MDS, which in turn may eventually transform to leukemia.^[12]

Secondary MDS can develop after exposure to certain treatments or environmental factors. Previous treatment with chemotherapy or radiation therapy for other cancers is one of the most recognized causes. When MDS develops after such treatments, it’s called therapy-related or secondary MDS. Environmental exposures can also contribute, including exposure to benzene and other organic chemicals, heavy metals, herbicides, pesticides, fertilizers, tobacco smoke, and ionizing radiation.^[12]

The transformation process itself involves the accumulation of additional genetic abnormalities over time. The cells in the bone marrow don’t just stay stable – they continue to acquire new mutations. In patients who transform to AML, specific genetic changes, such as mutations in the TP53 gene, occur more frequently and appear to drive the progression toward leukemia.^[4]

Factors That Increase Risk of Transformation

Several characteristics help doctors predict which patients are more likely to experience transformation. One of the most important factors is the percentage of blast cells in the bone marrow at the time of MDS diagnosis. Higher blast percentages indicate a greater risk of progression. MDS is sometimes classified into subtypes based on blast percentage: refractory anemia has less than 5 percent blasts, refractory anemia with excess blasts (RAEB) has 5 to 20 percent blasts, and RAEB in transformation has 21 to 30 percent blasts.^[2]

Certain genetic abnormalities in the cells significantly influence transformation risk. Patients with specific chromosomal problems, particularly those classified as high-risk cytogenetic abnormalities (changes in chromosome structure), face substantially higher chances of progression. For example, loss of chromosome 7 or part of chromosome 7 (monosomy 7) carries a worse outlook than some other genetic changes. In contrast, patients with a deletion in chromosome 5 (5q deletion) generally have a more favorable prognosis and lower transformation risk.^[1]

The severity of blood cell deficiencies also matters. Patients with more severe cytopenias (low blood cell counts) or deficiencies affecting multiple cell lines tend to have higher-risk disease. Performance status – a measure of how well a person can carry out daily activities – is another important predictor. Those who have significant limitations in their physical functioning due to their disease face poorer outcomes.^[4]

The time between MDS diagnosis and transformation also provides important information. Shorter transformation times are associated with worse overall outcomes. Some patients progress rapidly within months, while others may have stable disease for years before any transformation occurs, if it happens at all.^[4]

Signs and Symptoms to Watch For

Many people with MDS don’t experience obvious symptoms in the early stages. When symptoms do appear, they typically relate to the body’s shortage of healthy blood cells. Fatigue is one of the most common complaints, affecting up to nine out of ten people with MDS. This isn’t ordinary tiredness that improves with rest – it’s a profound, persistent exhaustion that doesn’t go away even after sleeping well.^[3]

As transformation approaches or occurs, symptoms may intensify or new ones may develop. Shortness of breath, especially during physical activity, often becomes more noticeable due to worsening anemia (low red blood cell count). The skin may appear unusually pale. Easy bruising or bleeding can occur due to low platelet counts, which help blood clot. Small red dots under the skin, called petechiae, may appear, especially on the legs or belly. These tiny spots result from bleeding under the skin.^[3]

Frequent infections become more common as white blood cell counts drop or these cells fail to function properly. The body’s ability to fight off bacteria, viruses, and other germs becomes compromised. Some people develop recurring fevers without obvious infection. As blast cells increase during transformation, some patients may experience bone pain, though this varies considerably from person to person.^[1]

Preventing or Delaying Transformation

While there’s no guaranteed way to prevent MDS from transforming to leukemia, certain treatment approaches aim to slow disease progression and reduce transformation risk. For patients with lower-risk MDS who have the 5q chromosomal deletion, a medication called lenalidomide has shown effectiveness in reducing the need for blood transfusions and may influence disease course.^[13]

Hypomethylating agents, including azacitidine and decitabine, are considered standard therapy for intermediate and high-risk MDS. These medications work by affecting how genes are expressed in cells and have demonstrated the ability to slow disease progression in some patients. While they don’t cure MDS, they may delay transformation and improve quality of life.^[13]

For eligible patients, allogeneic hematopoietic stem cell transplantation (also called bone marrow transplant) remains the only treatment approach with curative potential. This procedure replaces the patient’s diseased bone marrow with healthy stem cells from a donor. However, not everyone is a candidate for this intensive treatment. It’s typically reserved for younger patients with fewer other health conditions who have a suitable matched donor. Even among those who undergo transplantation, relapse remains a significant challenge.^[8]

Avoiding known risk factors before MDS develops can reduce the likelihood of developing the condition in the first place. This includes minimizing exposure to tobacco smoke, benzene and other organic chemicals, and unnecessary radiation. For people who need chemotherapy or radiation for other cancers, the benefits of these treatments generally far outweigh the small risk of developing secondary MDS years later.^[12]

How the Body Changes During Transformation

The transformation from MDS to acute leukemia represents a fundamental shift in how the bone marrow functions. In stable MDS, the bone marrow produces blood cells, but they’re abnormal and die prematurely. During transformation, immature blast cells begin multiplying rapidly without maturing into functional blood cells. These blast cells accumulate in the bone marrow, progressively crowding out the space needed for any normal blood cell production.^[6]

At the cellular level, additional genetic mutations accumulate in the abnormal cells. These changes affect genes that normally control cell growth, division, and death. The TP53 gene, which acts as a brake on uncontrolled cell growth, is frequently mutated in patients who transform to AML. When this protective gene stops working properly, cells can divide unchecked. Other genetic changes affect pathways that normally tell cells when to mature and when to stop dividing.^[4]

The bone marrow environment itself changes during transformation. The abnormal cells create an inflammatory environment that further suppresses any remaining normal blood cell production. This inflammation releases chemical signals that can damage healthy stem cells and create conditions that favor the survival and growth of the leukemic cells. The result is a self-perpetuating cycle where the diseased cells increasingly dominate the bone marrow.^[10]

As blast cells accumulate, they may eventually spill out of the bone marrow into the bloodstream in large numbers. In the blood, these cells can’t perform the normal functions of mature blood cells. White blood cell counts may appear elevated on blood tests, but these are non-functional blast cells rather than working immune cells. The person becomes increasingly susceptible to infections, anemia worsens dramatically, and bleeding problems may become severe.^[4]

Outlook After Transformation

When MDS transforms to acute myeloid leukemia, the prognosis becomes more serious. Patients who transform generally face a more challenging treatment course than those whose leukemia developed without prior MDS. The leukemia that arises from MDS tends to be less responsive to standard chemotherapy regimens compared to de novo AML – leukemia that appears without any prior blood disorder.^[1]

Several factors influence outcomes after transformation. Patients with better overall physical condition, as measured by performance status scales, tend to fare better than those who are more debilitated by their disease. The presence of certain genetic markers, particularly TP53 mutations, is associated with poorer survival. High-risk chromosomal abnormalities also predict worse outcomes after transformation.^[4]

In one study of 52 patients who transformed to AML, those who survived beyond 12 months had significantly lower performance scores, meaning they were functioning better physically. They also had fewer high-risk genetic features at the time of their original MDS diagnosis and at the point of transformation. The characteristics present at the initial MDS diagnosis, including the percentage of blasts in bone marrow and the specific MDS subtype, helped predict who would do better after transformation occurred.^[4]

Treatment response also varies considerably. Some patients achieve remission with intensive chemotherapy, while others show little or no response. For those who do respond to initial treatment, maintaining that response over time remains challenging. The five-year survival rate for all MDS patients is approximately 37 percent, and this number is lower for those who transform to AML.^[10]