How does leukemia begin?
When abnormal white blood cells appear in the bone marrow, they multiply rapidly and begin to crowd nut the normal cells that develop there After accumulating in the bone marrow• leukemic cells spill over into the blood and are carried to vital organs such as the lungs, liver. spleen. and kidneys
Leukemic cells may also cross the blood-brain barrier and invade the central nervous system (brain and spinal cord).
When the leukemic blasts begin to fill the marrow, production of healthy red cells, platelets, and white cells cannot be maintained As the number of normal cells decreases, symptoms appear Low red cell counts cause fatigue and pale skin Low platelet counts may result in bruising and bleeding problems If mature neutrophils and lymphoblasts are crowded out by the blasts, the child will have little or no defense against infections
Who gets leukemia?
Acute leukemia is the most common childhood cancer Although generally thought of as strictly a childhood disease, many more adults than children develop leukemia Each year in the United States, approximately 25.000 adults and 2,500 children will be diagnosed with acute leukemia.
Childhood leukemia is most commonly diagnosed at ages two to seven, with the highest incidence at approximately four years of age. In the United States, leukemia is more common in whites than in blacks and boys have a slightly higher incidence than girls Children with chromosomal abnormalities such as Down's syndrome, Bloom's syndrome, or Fanconi's anemia have a higher risk of developing leukemia than the general population. However, most children with these syndromes will not develop leukemia
Although the exact cause of childhood leukemia is a mystery, certain factors are known to increase the risk of developing the disease.
Genetic factors
It is known that persons with extra chromosomes (genetic material contained in cells) or certain chromosomal abnormalities have a greater chance of developing leukemia It is uncertain whether this is a cause or merely an association In cases where one identical twin has leukemia, the other twin has it 25 percent chance of developing the disease within one year, but this risk decreases with an older age at diagnosis and with time It is not known whether this is caused by an inherited trait or a simultaneous exposure to the same carcinogen Leukemia is not contagious, it cannot be passed from one person to another.
Environmental factors
Exposure to ionizing radiation and certain toxic chemicals may predispose individuals to leukemia Many Japanese who were exposed to fallout front (he atomic bomb during World War II and some of the people living near the Chernobyl accident in the Ukraine have developed leukemia. Chronic exposure to benzene has been associated with leukemia in adults. However, most children are not exposed to large amounts of radiation or industrial chemicals Risks to children from exposure to electromagnetic fields, herbicides pesticides, or pesticides are under investigation
The National Institutes of Health maintain a free hot line to answer questions on health and the environment, at 1-800-643-4794 For questions about FMF; (electromagnetic fields), call the Environmental Protection Agency's EMF Info Line at 1-800-363-2383. For information about the federal governments EMF research efforts, including public information materials developed by the EMF RAPID program, refer to the EMF RAPID home page on the World Wide Web http//www.niehs.nih.gov/emfrapid/home.htm
Viral factors
Viruses that cause leukemia in cows, cats, chickens, gibbons. and mice have been found Recently, a T-cell virus has been identified which causes a rare type of Leukemia-lymphoma in adults, however, no virus has been found which causes the types of leukemia commonly found in children
Currently, it is thought that a complex interaction among genetic, environmental, immunologic, and possibly viral factors predispose individuals to leukemia The most important point lee parents it) remember is that at present there is no way to predict or prevent leukemia
How is leukemia diagnosed?
A tentative diagnosis is made after a physical examination of the child and microscopic analysis of a Wood sample Physical findings may include
skin bruising or unusual bleeding, enlarged liver ,spleen or lymph nodes. ear or other infections (frequently resistant to treatment) weakness, and fever. Parents may describe irritability, night sweats, fatigue, bone pain, loss of appetite, and problems with balance. The blood test may show decreased red cells, decreased granulocytes, decreased platelets, and increased lymphocytes. There may be blast cells circulating in the blood.
To confirm a diagnosis of leukemia, bone marrow is sampled and tested. The bone marrow is examined microscopically by a pathologist, a physician who specializes in body tissue analysts. If more than 25 percent blasts are discovered in the marrow, the pathologist will confirm the diagnosis of leukemia. A portion of the bone marrow is also sent to a specialized laboratory, which analyzes many other features of the leukemic cells to determine which type of leukemia is present and whether the child has a low, average, or high risk of relapse. Risk levels help the oncologist choose the appropriate treatment for each child.
