Genetic flaws that increase the risk of the most common form of childhood leukaemia have been uncovered by British scientists.
The three variants each raise the risk by between 30% and 60%, said the Institute of Cancer Research team.
But they stressed that other things, such as childhood infections, may also play a role.
Leukaemia Research said the clues offered by the research, in the journal Nature Genetics, may improve care.
Leukaemia is the most common childhood cancer, with approximately 500 new cases each year in the UK, and Acute Lymphoblastic Leukaemia (ALL) accounts for roughly 85% of these.
Scientists believe that there is likely to be no single reason why a child develops the disease, but a combination of factors, perhaps including an inherited genetic ingredient in some cases.
Previous research has suggested that both a blood cell change that happens in the womb and other mutations. possibly triggered by common childhood infections. could be involved.
The latest research used technology which allows the entire DNA of leukaemia patients to be scanned for common features not present in apparently healthy children.
Small risk
The presence of each of the three variants was linked to a rise in the risk of the disease - although even then, the overall risk remained very small.
Professor Richard Houlston, who led the study, said: "These findings provide the first evidence that genetic make-up plays a major role in the risk of Acute Lymphoblastic Leukaemia, and insight into how the disease develops."
His colleague, professor Mel Greaves, said: "The new results should not be taken by parents or the public at large to mean that children develop leukaemia because of an accident of inheritance.
"Genetic risk factors are just one component of cause - finding the triggering exposures still remains a focus of intense effort."
The charity Leukaemia Research which part-funded the project, said that the research had uncovered "important clues" which could lead to "less punishing" treatments for children.
