Juvenille myelomonocytic leukaemia (JMML)

What is juvenille myelomonocytic leukaemia (JMML)?

JMML is a very rare childhood blood cancer.  Though JMML can be considered a chronic form of leukaemia, there are many distinguishing clinical features of JMML that are absent in the types of chronic leukaemia found in adults. The World Health Organisation has defined JMML as a mixed myelodysplastic and myeloproliferative disorder. Juvenile Chronic Myeloid Leukemia (JCML), Chronic Myelomonocytic Leukemia of Infancy, and Infantile Monosomy 7 Syndrome are all now classed as JMML.

About 75% of children diagnosed with JMML are discovered to have genetic abnormalities that are identified in laboratory testing at diagnosis.  There are three main types of mutations found in JMML. These mutations occur in a type of white cell known as a monocyte, which are a part of the body’s immune system.  These monocyte cells affected with JMML accumulate in the bone marrow interfering with production and function of healthy blood cells.  Overproduction of monocytic cells can infiltrate organs, including the spleen, liver, gastrointestinal tract, and lung.

Disease type, clinical presentation and age of the child when diagnosed are predicting factors in the child’s prognosis. Survival rates of children treated with stem cell transplantation are now being reported at over 50%.

How common is JMML?

JMML accounts for less than 1% of all childhood leukaemias diagnosed in the United States.

Who gets JMML?

JMML is a disease of childhood, more commonly diagnosed in children under the age of four, although the average age of diagnosis is two-years-old.

Children who have been diagnosed with neurofibromatosis 1, or Noonan syndrome are at an increased risk of developing JMML.

What are the causes of JMML?

The cause of JMML remains largely unknown. There are no proven environmental causes that contribute to the development of JMML.

What are the symptoms of JMML?

The symptoms of JMML result from the malfunctioning bone marrow and may include:

Abnormal red cell function or a lack of red cells (anaemia), which causes:

  • persistent tiredness and fatigue
  • weakness
  • shortness of breath with minimal exercise
  • looking pale.

Abnormal white cell function, often with low white cell counts, which causes:

  • recurring infections, especially chest infections
  • fevers
  • sore mouth due to mouth ulcers.

Abnormal platelet function, often with low platelet counts, which causes:

  • easy bruising
  • purpura – a rash of small red dots seen often on the lower limbs initially, due to small superficial capillary bleeds which are known as petechiae
  • tendency to bleeding from the nose and gums.

Children diagnosed with JMML can also present with enlarged lymph nodes, liver and spleen. Other symptoms and signs include developmental delay, decreased appetite and poor weight gain. Some of these symptoms may also be seen in other illnesses, including viral infections. It is important to see your doctor if your child has any symptoms that do not go away so that they can be examined and treated properly.

More information about JMML

» Diagnosis
» Treatment and side effects
» Living with JMML

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