Updated on Wednesday, July 25, 2007, 00:00 IST

Chicago, July 25: Most apparently random cases of autism may be just that, a function of freak genetic accidents, rather than a product of an inherited genetic predisposition that is passed down through generations, according to a study.

The authors of the study suggest that spontaneous mutations in the DNA of an afflicted child or their parent may play a much larger role than previously thought in sporadic cases of autism, where there is no family history of the devastating childhood developmental disorder.

The genetic origins of the neurological condition are still unclear, but US researchers recently reported that spontaneous mutations, or tiny glitches in the DNA, were common in about 10% of the autistic patients they studied. The pattern was particularly noticeable in cases of sporadic autism which is the most common form.

In the light of this finding, US investigators did a mathematical analysis of three databases on the incidence of autism to see if this new theory could account for the distribution of cases.

They concluded that a previously unrecognised pattern could be explained by assuming that spontaneous mutations are a significant cause of the disorder and that parents, especially women, who acquire the DNA glitches, have a 50% chance of passing it on to their child.

Bureau Report