The exact cause of myeloid malignancies in children has not been identified. Researchers, however, have gained a greater understanding of how specific changes in DNA can cause bone marrow cells to develop into leukemia and myelodysplastic syndromes.

Some forms of cancer are caused by DNA mutations that “turn on” oncogenes (genes that speed up cell division) or “turn off” tumor suppressor genes (genes that slow down cell division or cause cells to die at the right time). In children with leukemia and myelodysplastic syndromes, these mutations are normally acquired after birth. The mutations may occur from exposure to radiation or cancer-causing chemicals, but many times the mutations occur for no apparent reason.

One form of DNA abnormality, known as translocation, can cause myeloid malignancies to develop. Translocation is the transfer of DNA from one chromosome to another. This abnormality can turn on oncogenes, which causes rapid cell division. Although they occur less often, deletions (the loss of part of a chromosome) and inversions (the rearrangement of DNA in part of a chromosome) are other chromosome changes that can cause leukemia to develop.

In addition, researchers have identified a number of factors that may make a child more likely to develop myeloid malignancies including:

• Family history. Children who have a brother or sister with leukemia are at a higher risk of developing AML.
  
  
• Race. Hispanic children are at an increased risk of developing the AML.
  
  
• Gender. AML, myelodysplastic syndromes and JMML are more common in males.
  
  
• Exposure to cigarette smoke or alcohol before birth. Children who were exposed to cigarette smoke or alcohol in the womb have an increased risk of developing AML.
  
  
• Having a history of a myelodysplastic syndrome. Children with a history of a myelodysplastic syndrome are at a higher risk of developing AML.
  
  
• Having a history of aplastic anemia. Children with a history of aplastic anemia (a rare disease in which the bone marrow fails to produce enough blood cells) have an increased risk of developing AML.
  
  
• Chemotherapy. Children treated for other cancers with certain chemotherapy drugs are at an increased risk of developing AML and myelodysplastic syndromes.
  
  
• Exposure to very high levels of radiation. Children who have received radiation therapy as treatment for other forms of cancer have an increased risk of developing AML and myelodysplastic syndromes later in life. In addition, children exposed to radiation from atomic blasts, such as those in Japan during World War II, and nuclear accidents have an increased risk of developing AML and myelodysplastic syndromes.
  
  
• Environmental factors. Chemicals, such benzene (a solvent found in gasoline and cigarette smoke), can increase a child’s risk of developing myeloid malignancies. Long term exposure to other chemicals found in the petroleum and rubber industries can also place a child at higher risk. Several studies conducted by the National Cancer Institute (NCI) have investigated nearby high-voltage power lines as a risk factor for leukemias. To date, the results have indicated either no risk or only a slightly greater risk.
  
  
• Genetic syndromes. Children with certain genetic syndromes including Down syndrome and Fanconi’s syndrome have an increased risk of developing AML and myelodysplastic syndromes. Also, children with neurofibromatosis type 1 or Noonan’s syndrome are at an increased risk of developing JMML.