• Juvenile Myelomonocytic Leukemia (JMML)

    Juvenile myelomonocytic leukemia (JMML) is a rare type of blood cancer that occurs when bone marrow production of white blood cells becomes severely disregulated. In children with JMML, the bone marrow – the soft, spongy center of the bones responsible for creating blood cells – produces immature white blood cells that grow too rapidly and keep reproducing even when they run out of space. This crowds out healthy bone marrow cells and can lead to symptoms such as infections, anemia, and bleeding. Currently, the only cure for JMML is stem cell transplant.

    JMML Treatment at Dana-Farber/Boston Children's

    Patients with JMML are treated at Dana-Farber/Boston Children's through the Leukemia Treatment Program, one of the top programs worldwide for pediatric leukemia. Our program has been instrumental in refining treatments for childhood leukemia, which has resulted in improved cure rates and decreased side effects. We also have one of the largest and most experienced pediatric stem cell transplant programs in the U.S.

    Our leukemia treatment team includes internationally recognized pediatric hematologist/oncologists, hematopathologists (who have specialized expertise in correctly diagnosing pediatric hematologic malignancies like JMML), radiation oncologists, stem cell transplant physicians, and pediatric oncology nurses.

    What is leukemia?

    Leukemia is a blood cancer. It 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 (to carry oxygen); and platelets (to help blood clot and stop bleeding).

    • Read in-depth information on leukemia in children, including the different types of childhood leukemia.

    What are the causes and symptoms of JMML?

    JMML Causes

    About 90% of children diagnosed with JMML have been found to have specific genetic mutations that can be identified by a special laboratory. These mutations occur in a type of white blood cell known as a monocyte, which are a part of the body’s immune system. Children with Neurofibromatosis type 1 and Noonan syndrome are more likely to develop JMML.

    It’s important to understand that there’s nothing you could have done or avoided doing that would have prevented your child’s cancer from developing.

    JMML Symptoms

    Because JMML is a cancer of the blood-forming bone marrow, initial symptoms are often related to abnormal bone marrow function. The bone marrow is responsible for storing and producing about 95 percent of the body's blood cells, including the red blood cells, white blood cells, and platelets.

    While each child may experience symptoms of JMML differently, some of the most common include:

    • General fatigue or weakness
    • Recurrent infections: Although there may be an unusually high number of white blood cells on your child’s blood count, these white blood cells are immature and do not fight infection. Your child may have had several viral or bacterial infections over the past few weeks and may show symptoms of an infection such as fever, runny nose, and cough.
    • Bone and joint pain: Your child may experience pain in his bones and joints. This pain is usually a result of the bone marrow being overcrowded and "full."
    • Abdominal pain: Stomach aches may also be a symptom of leukemia. Leukemia cells can collect in your child’s kidney, liver, and spleen, causing enlargement of these organs. Pain in the abdomen may cause your child to lose his appetite and lose weight.
    • Swollen lymph nodes: Your child may have swelling in the lymph nodes under the arms, in the groin, in the chest, and in the neck. Leukemia cells may collect in the nodes, causing swelling.

    It is important to understand that the symptoms of JMML may resemble other blood disorders or medical problems. These are common symptoms of the disease but do not include all possible symptoms. Because many of these symptoms can also point to other conditions, it’s important to have your child evaluated by a qualified medical professional right away for an accurate diagnosis and prompt treatment.

    How is JMML diagnosed?

    The first step in treating your child is forming an accurate and complete diagnosis. JMML is often suspected due to results from a routine blood test conducted for other reasons.

    Your child’s physician may order a number of different tests including:

    • A complete medical history and physical exam.
    • Complete blood count (CBC): A measurement of size, number, and maturity of different blood cells in a specific volume of your child’s blood.
    • Additional blood tests may include blood chemistries, evaluation of liver and kidney functions, and genetic studies.
    • Bone marrow aspiration and biopsy: Marrow may be removed under local anesthesia. In aspiration biopsy, a fluid specimen is extracted from the bone marrow. In a needle biopsy, marrow cells (not fluid) are removed. These methods are often used together.
    • Chromosomal analysis: A test to help distinguish JMML from other leukemias and allow physicians to tailor treatment to the specific disease.
    • Spinal tap/lumbar puncture: A special needle is placed into the spinal canal via your child's lower back to access the area around the spinal cord. The pressure in your child’s spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (called CSF—the fluid that bathes your child’s brain and spinal cord) can be removed and tested for infection or other problems.

    There may be other diagnostic tests that your doctor will discuss with you depending on your child's individual situation. After we complete all necessary tests, our experts meet to review and discuss what they have learned about your child's condition. Then, we will meet with you and your family to discuss the results and outline the best possible treatment options.

    What are the treatments for JMML?

    JMML is not easily treated, though several therapies offer hope for a successful outcome. A stem cell transplant is the best option, though your child's team may consider other medications and procedures as well.

    Your child's treatment may include:

    • Stem cell (bone marrow) transplant: Stem cells are a specific type of cell from which all blood cells develop. They can grow into red blood cells to carry oxygen, white blood cells to fight disease and infection, and platelets to aid in blood clotting. Stem cells are found primarily in the bone marrow, but some also circulate in the blood stream.


      When your child's stem cells are replaced with those of a healthy and compatible donor, it is called allogeneic transplantation. The goal is for healthy stem cells from another person (whose tissue must be the same, or almost the same, as your child's) to restore your child's normal blood production.

      All children undergoing a stem cell transplant for JMML must receive high-dose chemotherapy to make room in their bone marrow for the new stem cells. Called a “conditioning regimen” this chemotherapy accomplishes several important things. It suppress the body’s immune system to prevent rejection of the stem cells, and it destroys cancer cells in the body. Like a blood transfusion, stem cells are given to a child through an intravenous (IV) catheter. Children are awake through this painless process. It generally takes two to four weeks for the stem cells to multiply and make new blood cells. This is called engraftment. Side effects, such as fever, chills, and shortness of breath, can accompany the infusion of stem cells. More significant complications, including graft rejection and graft-versus-host disease (a condition in which the donor’s immune cells attack the patient’s body), can occur following the transplant.

    • Chemotherapy: Chemotherapy is a drug treatment that works by interfering with the cancer cell's ability to grow or reproduce. Standard chemotherapy alone is not adequate for curing JMML but may be used to decrease symptoms while your child is prepared for a stem cell transplant.

      Different groups of chemotherapy drugs work in different ways. Your child may receive chemotherapy orally, as a pill to swallow; intramuscularly, as an injection into the muscle or fat tissue; intravenously, as a direct injection into the bloodstream or IV; or intrathecally, as a direct injection into the spinal column through a needle.

      While chemotherapy can be quite effective in treating certain cancers, the drugs cannot differentiate normal healthy cells from cancer cells. As a result, there can be adverse side effects during treatment. Being able to anticipate these side effects can help the care team, child, and family prepare (and, in some cases, prevent) these complications from occurring, if at all possible.

    • Biologic medicines: Biological therapy refers to a wide range of substances that may be able to involve the body's own immune system to fight cancer or lessen harmful side effects of some treatments.

    Of course, your child's team of doctors will help determine the best approach for your child's unique situation, based on a number of factors including:

    • Your child's age, overall health, and medical history
    • The extent of the disease
    • Your child's tolerance for certain medications, procedures, or therapies
    • How your child's doctors expect the disease to progress
    • Your opinion and preferences

    What is the latest JMML research?

    Scientists at Dana-Farber/Boston Children's are on the front lines of research involving pediatric cancers and blood disorders, including JMML.

    Our Stem Cell Transplant Center is one of eight institutions nationwide investigating the use of umbilical cord transplantation as a novel method for preventing graft versus host disease, a serious complication that occurs when transplanted cells do not recognize the tissues and organs of the recipient's body and react hostilely. The result of this treatment approach, if it continues to be successful, will be that the degree of match between donor and recipient need not be close, increasing the pool of potential donors for each patient. This could also eliminate the need for long-term drug therapy traditionally needed to treat graft versus host disease.

    Clinical trials

    Clinical trials, or research studies evaluating new treatment approaches, are a major offering at Dana-Farber/Boston Children’s. Clinical trials are very important for children with hard-to-treat or relapsed conditions.

    Clinical trials at Dana-Farber/Boston Children's are designed to investigate new therapies for refractory or relapsed leukemia, novel combinations of chemotherapy drugs, and promising new treatment agents. Our researchers are conducting randomized clinical studies to reduce treatment intensity to lessen side effects and to test more intense and newer therapies to improve cure rates.

    We connect patients with trials available through collaborative groups such as the Children's Oncology Group (COG) and the Pediatric Oncology Experimental Therapeutics Investigators' Consortium (POETIC). We are the New England Phase I Center of the Children's Oncology Group. If your child has a hard-to-treat cancer, he or she may be eligible for a number of experimental therapies available through these groups or from one of our independent clinical investigators.

    The Children's Oncology Group is a consortium of cancer treatment centers across the United States, Canada, and other countries that conduct studies of nearly every kind of pediatric cancer. Our participation in this group gives children with cancer unparalleled access to the newest clinical trials.

    What is the long-term outlook for JMML?

    Despite advances in treatment, JMML remains difficult to cure. Without treatment, the five-year survival rate is dismal (about 5%).

    Stem cell transplantation has proven to be a successful treatment; however, the relapse risk is significant—about 50 percent—following a transplant. If JMML recurs after a stem cell transplant, a second transplant may be an option.

    As with any cancer, prognosis and long-term survival varies greatly. Prompt medical attention and aggressive therapy are important for the best prognosis, and continuous follow-up care is essential. New methods are continually being discovered to improve treatment and decrease side effects of the treatment for the disease.

    What care will my child need long-term?

    Some children who are treated for JMML and other pediatric cancers can experience significant long-term problems as a result of their treatment. All kids who have been treated for cancer require ongoing, specialized care.

    Through the David B. Perini Jr. Quality of Life Clinic, our cancer survivorship clinic, childhood cancer survivors receive a comprehensive follow-up evaluation from their cancer care team. In addition to meeting with your pediatric oncologists, your child may see one of our endocrinologists, cardiologists, neurologists, neuro-psychologists, or alternative/complementary therapy specialists. We also offer patient and family education, psychosocial assessment, genetic counseling, reproductive counseling, and opportunities to speak with other childhood cancer survivors.

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