An inherited gene mutation seems to increase the risk for one of the most common forms of leukemia, researchers say.

Researchers identified the gene by testing the genes of a family with seven cases of chronic lymphocytic leukemia, or CLL, the most common adult leukemia in North America.

"Our findings identify for the first time a gene that appears to be associated with hereditary CLL," said study co-author John Byrd, a professor of internal medicine at Ohio State University and a specialist in the disease.

The findings show how the gene, called DAPK1, is important in the disease. Potentially, the gene could be re-activated as a therapy, Byrd said.

It helps trigger the death of cells before they become cancerous. The mutated version interferes with the gene's protective function, the team reported in Friday's issue of the journal Cell.

"This inherited change is remarkably subtle," the study's co-principal investigator, Albert de la Chapelle, professor of molecular virology, immunology and medical at Ohio State, said in a release.

"Recently, many cancer geneticists have come to believe that such subtle changes are common causes of cancer, and this is one of the first, strong examples of that principle."

A second mutation, which the researchers said is not inherited, turns the gene off completely, leading to tumour growth.

About 10 per cent of cases of CLL occur in people who have a relative with the disease, with the other 90 per cent thought to be random.