Researchers have identified a genetic trait that appears to boost the risk that a child will develop an often-fatal cancer that targets the nervous system.

The findings don't point toward a treatment, but they do give scientists more insight into neuroblastoma, said study co-author Dr. John Maris.

"We've learned a lot more about the underlying cause and the biology of the disease," said Maris, director of the Center for Childhood Cancer Research at the University of Pennsylvania School of Medicine, in Philadelphia.

Although not well known, neuroblastoma is the second most common form of cancer in children after leukemia, Maris said. The American Cancer Society estimates that about 650 children develop it each year in the United States.

Neuroblastoma strikes young children and infants, and is fatal in about two-thirds of the cases, Maris said.

Tumors develop in the nervous system and can appear along the spine and in the neck, chest and abdomen, he said. Many tumors begin in the adrenal gland, which produces adrenaline in the body.

Most children have an aggressive form of the disease and must be treated with intensive therapy, involving strategies such as chemotherapy, radiation and stem-cell transplants, Maris said.

The disease appears to run in families, but only in about 1 percent of cases, he said. In those cases, a child survives the cancer and grows up to have a child with the disease.

In the new study, researchers looked at genetic samples from hundreds of white children with the disease and compared them with those of children who didn't have it.

They found that a specific "copy number variation" -- a kind of genetic trait -- doubles the chances that a child will develop the cancer. A report on the findings appears in the June 18 issue of Nature.

People inherit half their DNA from their mothers and half from fathers, but errors occur along the way. Human's genetic replication machinery functions, in a sense, like a malfunctioning copy machine that occasionally spits out too many -- or two few -- copies of a page while duplicating a stack of documents.

When DNA is copied incorrectly, the result is known as a copy number variation.