Myelodysplastic syndrome

At Boston Children's Hospital, we understand how overwhelming a diagnosis of myelodysplastic syndrome can be. Right now, you probably have a lot of questions. How dangerous is this condition? What is the very best treatment? What do we do next?

We’ve tried to provide some answers to those questions in the following pages, and our expert pediatric subspecialists can explain your child’s condition fully when you meet with us.

What is myelodysplastic syndrome?

Myelodysplastic syndrome (MDS) is a rare disease of the blood. Most of the time it develops in older patients (over 60 years old), but it can occur at any age and affect children as well. MDS develops in the bone marrow, the soft, spongy center of the long bones that produces the three major blood cells:

• white blood cells to fight infection
• red blood cells that carry oxygen
• platelets that help blood clot and stop bleeding

MDS occurs when the bone marrow does not properly produce sufficient numbers of healthy red blood cells, white blood cells and platelets. With this disease, the blood cells lose their ability to mature and function properly.

In normal bone marrow, the growth and development of blood cells are carefully controlled to produce the correct number of each type of blood cell to keep the body healthy.

All blood cells (white blood cells, red blood cells and platelets) are made from the start in the bone marrow from a single type of cell called a stem cell. Stem cells make up a very small portion of all the cells in the bone marrow. When more cells are needed, the bone marrow activates stem cells to rapidly produce more blood cells.

• In MDS, this process of maturation from a stem cell into a mature cell is disturbed.
• Red and white blood cells may mature, but not normally or in insufficient numbers.
• Sometimes the number of immature blood cells, called blasts, increases.
• As the disease progresses, these blasts continue to increase and invade the bone marrow, preventing it from working effectively.

MDS used to be called “smoldering leukemia” or “pre-leukemia,” but only about one-third of cases of MDS actually progress to leukemia. Leukemia is a cancer of the blood and bone marrow. As you read further below, you will find general information about MDS. If you would like to view summary information about cancer first, see the cancer overview.

What causes MDS?

Pediatric MDS is a very rare condition. It only occurs in 4 out of every million children.

• Most of the time MDS develops in previously healthy children, with no identifiable cause.
   
• In some patients, MDS occurs secondary to some other event or illness. We call this secondary MDS. It can occur in patients who have had chemotherapy or radiation therapy for another illness or malignancy.
   
• Other patients have rare underlying conditions of their bone marrow called inherited bone marrow failure disorders.

Many patients with MDS have a chromosomal abnormality associated with the disease; however, these changes are not inherited from someone in the family. Instead, these abnormalities are changes in the chromosomes that exist only in the diseased blood and bone marrow cells.

• The most common abnormalities occur in chromosomes 5 and 7 and 8.
   
• These acquired chromosomal alterations are thought to play a role in the development of the disease.
   
• Certain congenital chromosomal disorders, including Down syndrome, are also associated with an increased risk for the development of childhood MDS and leukemia.

What are the different types of MDS?

There are two different major categories of myelodysplastic syndrome: primary and secondary.

• In primary MDS, the disease occurs for no known reason. This group also includes MDS that runs in families.
   
• In secondary MDS, the disease is caused by another condition. This group includes MDS resulting from previous chemotherapy or radiation therapy. It also includes MDS caused by inherited bone marrow failure disorders, such as Fanconi anemia.

Physicians have identified several sub-types of MDS, based on how blood and marrow cells appear under the microscope. However, they are largely classified by the fraction of blasts (immature blood cells) found in the marrow and blood. The subtypes that have been identified in children are somewhat different from the ones physicians have identified for adults and older people.

The types of MDS in children are:

• Refractory cytopenia (RC): less than 5 percent blasts in bone marrow
• Refractory anemia with excess blasts (RAEB): 5-20% of blasts in the bone marrow
• RAEB in transformation (RAEB-t): 21-30% of blasts in the bone marrow

When the amount of blasts in a child’s bone marrow exceeds 30 percent, the condition is considered to be acute myelogenous leukemia.

When MDS predominantly affects white blood cells, the immature forms of white blood cells (blasts) increase in number, and the number of mature white blood cells typically decrease.

• It is normal to have a small number of blasts even in a healthy bone marrow (up to 5%).
   
• However, in MDS patients the percentage of blasts often increases over 5%, which is then called Refractory Anemia with Excess Blasts (RAEB). 
   
• If the blasts become especially numerous and the disease gains more and more the appearance of acute myeloid leukemia (AML), the disease is called Refractory Anemia with Excess Blasts in transformation (RAEB-t).
   
• AML is a type of leukemia characterized by an increase in a particular type of white blood cell. AML that has developed after MDS is, in general, much harder to cure than "de novo" AML (regular AML that started anew without any underlying MDS or other disease).

In adults other forms of MDS have been described and include:

• Refractory anemia (RA): less than 5 percent blasts in bone marrow. The developing red cells in the bone marrow are often unable to process iron properly. RA is the adult equivalent to the childhood RC mentioned above.
   
• Refractory anemia with ringed sideroblasts (RAS): less than 15 percent blasts. Developing red cells in the bone marrow are unable to process the iron that normally goes into hemoglobin. The iron is then deposited inside the red blood cells and forms a "ring" that can be seen under a microscope. This form of MDS is common in older people but almost never occurs in children.
   
• Refractory cytopenia with multi-lineage dysplasia (RCMD): less than 5% blasts in the bone marrow. Two or all three of the developing bone marrow cells (red cells, white cells and platelets) are not maturing and developing properly and appear abnormal (dysplastic). The significance of this degree of dysplasia in children remains unclear.
   
• MDS with isolated del (5q) (5q- syndrome): less than 5% blasts in the bone marrow. The syndrome is characterized by a specific abnormality in one of the chromosomes, where a part of the 5^th chromosome is deleted (absent). This syndrome does usually not occur in children.

Symptoms

What are the symptoms of MDS?

Because MDS is a disease of the blood-forming tissue called the bone marrow, initial symptoms are often related to abnormal bone marrow function. The bone marrow is responsible for producing the body's blood cells, including the red blood cells, white blood cells, and platelets. Sometimes MDS is discovered when a child is having a routine blood test for other reasons.

The most common symptoms of MDS include:

• Anemia: Anemia occurs when red blood cells are not produced properly or in inadequate numbers and the amount of oxygen-carrying protein hemoglobin is decreased. With anemia, the child may appear tired or pale, and may breathe faster to compensate for the decreased ability to deliver oxygen to her body.
   
• Bleeding: In MDS, platelets, which help stop bleeding, are often reduced. Therefore, patients with MDS may experience bruising or abnormal bleeding (prolonged nose bleeds, bleeding from the gums).
   
• Infections: In many cases of MDS, the type of white blood cells that fight off bacterial infections (neutrophils) can be very low. This condition is called neutropenia. Neutropenia may be the result of a failure of immature precursors in the bone marrow to mature or an increase in blasts that crowds out normal cells in the bone marrow. In other cases of MDS, the white cell count can be unusually high.

In both cases, there are not enough normal healthy white blood cells present in the blood to fight infection. The child may have had repetitive infections or even serious infections with high fevers.

It is important to understand that the symptoms of MDS may resemble other blood disorders or medical problems, some of which are very common and easy to treat, others of which could be more serious. The symptoms listed above are common presentations of the disease, but do not include all possible symptoms.

Your child may experience symptoms differently. Therefore, it is important to be evaluated by a physician to obtain an accurate diagnosis. Always consult your child's physician if you have concerns. 

Questions to ask your child’s doctor

After your child is diagnosed with MDS, you may feel overwhelmed with information. It can be easy to lose track of the questions that occur to you.

Lots of parents find it helpful to jot down questions as they arise—that way, when you talk to your child’s doctors, you can be sure that all of your concerns are addressed.

If your child is old enough, you may want to suggest that she write down what she wants to ask her health care provider, too.

Some of the questions you may want to ask include:

• What type of myelodysplastic syndrome does my child have?
• How will my child’s symptoms be managed?
• Can my child receive a stem cell transplant?
• How long will my child need to be in the hospital?
• What are the possible short- and long-term complications of treatment? How will they be addressed?
• What is the likelihood of cure?
• What services are available to help my child and my family cope?

FAQ  

Q: Where will my child be treated?

A: Children treated through Pediatric Myelodysplastic Syndromes Specialty Care will receive outpatient care through Children’s Hospital Boston. If your child receives a stem cell transplant, she will see doctors at the Jimmy Fund Clinic at Dana Farber and will stay in Children’s specialized stem cell transplant unit.

Q: What services are available to help my child and my family cope?

A: We offer a variety of support services to help you, your child and your family get through this difficult time.

Q: What is the expected outcome after treatment for myelodysplastic syndromes?

A: A child’s prognosis greatly depends on:

• the specific diagnostic category of MDS, chromosomal abnormalities, and the number of blasts in the blood and bone marrow
• whether the MDS is a primary disorder or secondary to another disease
• the availability of a suitable bone marrow transplantation donor

Your child’s physician is available to answer questions about treatment options and outcomes.