Investigating a Cluster of Cases of Leukemia among Children in Nevada
CDC worked with the Nevada State Health Division (NSHD) to conduct a study to identify environmental exposures in the Churchill County, Nevada community, where 15 cases of childhood leukemia had been diagnosed from 1997–2002. CDC found that people living in Churchill County had higher levels of some metals in their urine than the U.S. population. Two of these metals were tungsten and arsenic. CDC also found that the levels of these metals in families in which a child had leukemia (case families) were not different from the levels found in families in which no children had leukemia (comparison families).
In collaboration with St. Jude Children's Research Hospital, CDC tried to find out if there were genetic similarities or differences between case children and comparison children so that these factors could be examined. CDC found a genetic difference, or variant, in a gene that contains instructions for making special proteins called sulfite oxidase enzymes. Without this and other enzymes, the body may not be able detoxify chemicals (i.e., to change a harmful substance into a safer form).
It is not clear how inactivation of this enzyme might relate to childhood leukemia. CDC found no evidence that a genetic factor caused the cases of leukemia in Churchill County. It is also not possible to say that the presence of this genetic variant can predict who will get leukemia. That's because all of the case children and 40 percent of comparison children had this variant, and many of these children were also exposed to tungsten. More research may be useful to find out if having the gene variant increases children's susceptibility to leukemia and what other factors, if any, must exist to cause leukemia. This study is an important first step in answering these and other difficult questions about childhood leukemia in Churchill County.
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