Juvenile Myelomonocytic Leukemia: Symptoms & Treatment

Risk Factors, Gene Abormalities, Stem Cell Transpants and JMML

What is Juvenile Myelomonocytic Leukemia (JMML) and what should you know?. Istockphoto.com/Stock Photo©MaksiMages

What is juvenile myelomonocytic leukemia (JMML) and how is it treated?

Juvenile Myelomonocytic Leukemia (JMML) - Definition

Juvenile myelomonocytic leukemia (JMML) is a rare type of aggressive blood cancer that affects infants and young children; accounts for less than 1% of childhood leukemias. The average age of children at diagnosis is 2 years old, and it is uncommon to see cases in children older than six years of age.

It is 2 ½ times more common in boys than girls.

JMML has also been referred to as juvenile chronic myelogenous leukemia (JCML), juvenile chronic granulocytic leukemia, chronic and subacute myelomonocytic leukemia, and infantile monosomy 7.

How it Happens

JMML occurs when changes (for example, mutations) accumulate in the DNA of a type of stem cell in bone marrow that typically gives rise to a type of cell known as a monocyte. The changes cause the affected cell to multiply out of control.

As the numbers of these abnormal cells increase, they begin to take over the bone marrow. Over time, they will interfere with the bone marrow’s main job, which is to produce red blood cells, healthy white blood cells and platelets.

Risk Factors

Researchers do not know what causes the DNA changes that lead to JMML, but new studies are suggesting that it may be inherited from the child’s parents.

Children with neurofibromatosis type I and Noonan syndrome have an increased risk of developing JMML, with up to 14% of children diagnosed with JMML having Noonan syndrome.

Signs and Symptoms of JMML

The signs and symptoms of JMML are related to the accumulation of abnormal cells in the bone marrow and organs. They may include:

  • Pale skin
  • Frequent infections or illness
  • Abnormal bleeding
  • Swollen abdomen related to enlarged spleen (splenomegaly) and enlarged liver
  • Fevers
  • Rash
  • Decreased appetite
  • Cough
  • Developmental delays

These can also be signs and symptoms of other non-cancerous conditions. If you are concerned about your child's health, the best thing to do is visit your healthcare provider.

Diagnosing JMML

To diagnose JMML, doctors will examine the results of blood tests as well as bone marrow aspiration and biopsy. Certain findings will indicate JMML:

  • An elevated white blood cell count, in particular high monocytes
  • Low red blood cell count (anemia)
  • Low platelet count (thrombocytopenia)
  • Abnormalities in chromosome 7

The lack of the Philadelphia chromosome will help determine that the disease is not chronic myelogenous leukemia (CML).

Disease Paths

There are 3 somewhat distinct ways in which this type of leukemia acts.  In the first type the disease is rapidly progressive.  In the second type, there is a transient period when the child is stable, followed by a rapidly progressive course.  In the third type, children may improve and remain only mildly symptomatic for up to 9 years, at which time the disease becomes rapidly progressive without treatment.

Treatment of JMML

The primary treatment for JMML is a stem cell transplant, but on occasion on treatments are used as well.


The role of surgery in the treatment of JMML is controversial. One common study protocol (The Children’s Oncology Group- COG) recommends a splenectomy (spleen removal) on all children with the disease who have enlarged spleens. The other main JMML treatment protocol (European Working Group on Myelodysplastic Syndrome in Childhood- EWOG-MDS) leaves it up to the patient’s physician to decide. It is unknown if the long-term benefit of this procedure outweighs the risks.


On the whole, JMML tends to have a poor response to chemotherapy. Purinethol (6- Mercaptopurine) and Sotret (isotretinoin) are drugs that have been used with a small measure of success. Because of its limited benefit in the treatment of JMML, chemotherapy is not the standard.

Stem Cell Transplant

Allogeneic stem cell transplant is the only treatment that can offer a long-term cure for JMML. Research has found similar success rates with either matched family stem cell donors or matched unrelated donors.

The rate of relapse after stem cell transplant for JMML may be between 30% and 50%, which is very high. Relapse occurs an average of 3 ½ months following transplant, and almost always within a year. However, despite these discouraging numbers, patients often achieve a cure with a second stem cell transplant.

Despite the need for aggressive treatment, children with JMML are doing much better with advances such as stem cell transplants.  It was found in one study that the 5-year survival rate for children who received matched family stem cells was 55%, with a 5-year survival rate of 49% in those who had unrelated donors, and this treatment is improving all the time.

The Bottom Line

As a parent, one of the most difficult things to imagine is your baby or child getting sick. This type of illness can put a tremendous strain on the child, the parents and the siblings. You may be struggling to explain a complicated situation to your children, without being able to wrap your head around it yourself.

Take advantage of any support groups or resources offered by your cancer center, as well as your loved ones, friends, family and neighbors. While you and your family may be experiencing a wide range of emotions and feelings, it is important to remember that there is hope for a cure and that some children with JMML go on to lead healthy and productive lives.


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Locatelli, F., Nollke, P., Zecca, M. et al. Hamtopoietic stem cell transplantation (HSCT) in children with juvenile myelomonocytic leukemia (JMML): results of the EWOG-MDS/EBMT trial. Blood. 2005. 105(1):410-9

National Cancer Institute. PDQ Cancer Information Summaries. Health professional version. Childhood Acute Myeloid Leukemia/Other Myeloid Malignancies Treatment (PDQ®). Published online 09/29/15. http://www.ncbi.nlm.nih.gov/books/NBK66019/#CDR0000062896__78

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