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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 defines it from types of chronic leukaemia found in adults.

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 cells affected with JMML accumulate in the bone marrow and also in the spleen, interfering with production and function of healthy blood cells.

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

There are a group of diseases that have characteristics of both myelodysplastic syndromes (abnormal bone marrow cells producing too few blood cells) and myeloproliferative neoplasms (abnormal bone marrow cells producing too many blood cells).  Juvenile myelomonocytic leukaemia (JMML) is included in this group of diseases.  JMML is a serious form of chronic leukaemia. JMML accounts for less than 1% of all childhood leukaemias diagnosed.

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

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

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

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

Abnormal platelet function, often with low platelet counts, 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.

Due to the rarity of JMML, a consensus on the standard treatment for JMML is not clear. Standard chemotherapy has proven to be effective in a small number of children.  Chemotherapy protocols utilised to treat children with AML have been given to children with JMML and resulted with remission.  However due to JMML being a resistant disease relapse is common.  A splenectomy (removal of spleen) may be suggested by your child’s treating specialist to help manage the disease.

Currently an Allogeneic (donor) Stem Cell transplant is the only curative option for children with JMML.  Around 50% of children who undertake a transplant obtain long term remission.  However, unfortunately a high number of children relapse with JMML post their transplant.  Your treating specialist will discuss treatment options with you if your child relapses.