Myelodysplastic syndrome is a blood disorder where your bone marrow makes abnormal cells

Myelodysplastic syndrome (MDS) is a group of disorders in which your bone marrow — the spongy tissue inside your bones that makes blood cells — produces cells that are malformed or don't work properly. Over time, these abnormal cells can crowd out healthy ones, leading to low counts of red blood cells, white blood cells, or platelets. This can cause anemia, infections, or bleeding problems.

MDS is sometimes called a "pre-leukemia" because in some people it progresses to acute myeloid leukemia (AML), a faster-growing blood cancer. However, many people with MDS live for years without it becoming leukemia, and some never develop it at all. The course of the disease varies widely depending on how many abnormal cells are present and what genetic changes are found in those cells.

MDS typically develops slowly and is most common in adults over 65, though it can occur at any age. It is not something you catch from another person — it develops when something goes wrong in the DNA of blood-forming cells in the bone marrow.

Key Takeaways

  • Myelodysplastic syndrome occurs when bone marrow produces abnormal blood cells that don't function properly or crowd out healthy cells.
  • Common symptoms include fatigue, shortness of breath, frequent infections, and unusual bleeding or bruising due to low blood cell counts.
  • Diagnosis requires a blood test and a bone marrow biopsy, in which a doctor removes a small sample of bone marrow to examine the cells under a microscope.
  • Doctors use a scoring system to determine how aggressive the MDS is and what treatment approach may be needed.
  • Treatment options range from monitoring without immediate treatment to chemotherapy or stem cell transplant, depending on the type and severity of MDS.

How doctors identify myelodysplastic syndrome

Your doctor will start by ordering a complete blood count (CBC), a standard blood test that measures the number of red blood cells, white blood cells, and platelets. In MDS, one or more of these counts is typically low. The blood sample may also show abnormal-looking cells when examined under a microscope.

If the CBC suggests MDS, your doctor will perform a bone marrow biopsy. During this procedure, a needle is inserted into the hip bone (or sometimes the breastbone) to withdraw a small sample of bone marrow. This sample is then examined under a microscope to look at the shape and number of cells and to check for genetic abnormalities. The biopsy is the key test that confirms MDS and helps determine which type you have.

Your doctor may also order additional tests, such as cytogenetics (which looks at the chromosomes in the cells) or flow cytometry (which identifies cell types using special markers). These tests help classify the MDS and predict how it may behave.

Symptoms that may lead to an MDS diagnosis

Many people with early MDS have no symptoms and discover it only through routine blood work. Others notice signs related to low blood cell counts. Anemia — too few red blood cells — causes fatigue, weakness, shortness of breath, or dizziness. Thrombocytopenia — too few platelets — leads to unusual bruising, nosebleeds, or bleeding gums. Leukopenia — too few white blood cells — increases the risk of infections that seem to come more often than usual.

Some people experience a combination of these symptoms. Others may feel generally unwell or notice they tire more easily than before. Because these symptoms can have many causes, a doctor will run tests to determine whether MDS is responsible.

How MDS is classified and scored

Once MDS is confirmed, doctors assign it a risk category based on how many abnormal cells are present and what genetic changes are found. The most widely used system is the Revised International Prognostic Scoring System (IPSS-R), which places MDS into five risk groups: very low, low, intermediate, high, and very high. This score helps predict how quickly the disease may progress and guides treatment decisions.

A "very low" or "low" risk score means the disease is likely to progress slowly, and your doctor may recommend watching and waiting rather than starting treatment right away. A "high" or "very high" score suggests faster progression and a higher chance of developing acute leukemia, so treatment may begin sooner.

Your doctor will explain your specific risk category and what it means for your outlook and treatment plan. The score can change over time as the disease evolves, so you will have repeat blood tests and bone marrow biopsies to monitor it.

The difference between MDS and acute leukemia

MDS and acute myeloid leukemia (AML) are related but distinct. In MDS, the abnormal cells are still partly immature and the disease develops slowly. In AML, the cells are more immature (called blasts) and multiply much faster, causing symptoms to appear and worsen quickly. A key difference is the percentage of blasts in the bone marrow: MDS typically has fewer than 20 percent blasts, while AML has 20 percent or more.

Some people with MDS eventually develop AML — this is called "transformation." Others live for many years with stable MDS and never transform. Your risk category helps predict the likelihood of transformation, but it is not certain.

What happens after diagnosis

After your diagnosis is confirmed and your MDS is classified, your doctor will discuss a treatment plan. For low-risk MDS, the plan may be "watch and wait" — regular blood tests and bone marrow biopsies to track the disease without starting treatment unless it worsens. This approach avoids the side effects of treatment when the disease is not immediately threatening.

For higher-risk MDS, treatment options may include medications like azacitidine or decitabine, which can slow the growth of abnormal cells. Other options include lenalidomide for certain types of MDS, or chemotherapy if the disease is progressing quickly. In some cases, a stem cell transplant (also called a bone marrow transplant) may be considered, especially in younger patients with high-risk disease.

Your doctor will explain the goals of treatment, what to expect from each option, and the potential side effects. Treatment plans are tailored to your age, overall health, and the specific characteristics of your MDS.

Living with MDS and follow-up care

People with MDS need regular follow-up appointments to monitor blood counts and watch for changes in the disease. How often you see your doctor depends on your risk category and whether you are receiving treatment. Some patients have appointments every few weeks, while others may go several months between visits.

During follow-up visits, your doctor will order blood tests and may repeat bone marrow biopsies to assess how the disease is progressing. If your blood counts drop significantly, you may need transfusions of red blood cells or platelets to manage symptoms. If infections become frequent, your doctor may prescribe antibiotics or other preventive measures.

Many people with MDS benefit from support groups, counseling, or speaking with others who have the condition. Your doctor or hospital social worker can connect you with these resources.

Frequently Asked Questions

Is myelodysplastic syndrome cancer?

MDS is considered a blood disorder and a type of cancer because it involves abnormal cells in the bone marrow. However, it behaves differently from many other cancers — it often grows slowly and may not require immediate treatment. Some people with MDS live for years without it becoming acute leukemia.

Can MDS be cured?

A stem cell transplant offers the only potential cure for MDS, but it carries significant risks and is typically considered for younger, healthier patients with high-risk disease. For many people, the goal of treatment is to manage symptoms, slow progression, and maintain quality of life rather than achieve a cure.

What causes myelodysplastic syndrome?

In most cases, the cause of MDS is unknown. It develops when mutations occur in blood-forming cells in the bone marrow. Some people develop MDS after chemotherapy or radiation for another cancer, but most cases occur without a clear trigger.

How long can you live with MDS?

Life expectancy varies widely depending on the risk category, age, and overall health. Some people with low-risk MDS live for many years with minimal progression. Others with high-risk disease may progress more quickly. Your doctor can discuss what the research shows for your specific type and risk level.

Will MDS turn into leukemia?

Not everyone with MDS develops leukemia. The risk depends on your risk category — people with low-risk MDS have a much lower chance of transformation than those with high-risk disease. Your doctor will monitor you for signs of progression and adjust treatment if needed.