WASHINGTON - Tiny gene mutations that occur spontaneously increase the risk of autism much more than previously thought, according to a study published Thursday.
These rare mutations were found to be 10 times more prevalent in people plagued by autism than in other individuals, said lead researcher Jonathan Sebat of the Cold Spring Harbor Laboratory in New York state.
The also suggest that many different genetic anomalies can eventually generate the same type of sporadic autism.
Sedat and 30 colleagues from several institutions reported their findings in the online edition of Science Express.
"Our results show conclusively that these tiny glitches are frequent in autism, occurring in at least 10 percent of cases, and primarily in the sporadic form of the disease, which accounts for 90 percent of affected individuals," said Sedat.
"Understanding such sporadic autism will require different genetic approaches and stepped-up recruitment of families in which only one individual has the disease," he said.
The study, funded by the National Institute of Mental Health (NIMH), examined genetic material from 264 families.
Researchers found spontaneous mutations in 14 out of 195 people with autism disorders, compared with two out of 196 unaffected individuals in good health.
Among the 14 autism patients with mutations, 12 were the only members of their family afflicted by the disease, while two belonged to families with at least one other afflicted sibling.
The study noted that the mutations were not frequently found in autism cases in families with more than one affected member.
"These structural variations are emerging as a different kind of genetic risk for autism than the more common sequence changes in letters of the genetic code that we've been looking for," said NIMH director Thomas Insel.
"These findings certainly complicate the search for genes contributing to autism. These are rare changes, dispersed across the genome, and they tell us that autism may be the final common path for many different genetic abnormalities," he said.
"Failure to develop social skills and repetitive and obsessive behavior may in fact be the consequence of a reaction to many different cognitive impairments," the researchers noted.
03/16/2007 02:40 GMT