DEAR DOCTOR K: I've heard that scientists have discovered genes that cause autism. Could this lead to a cure?

DEAR READER: Autism is a disorder of child development. Kids with autism have difficulty communicating and forming social relationships.

The studies you are referring to identify genes that increase the risk of autism, and could someday lead to a cure. I think of these studies as the first steps down what is going to be a long road. Nevertheless, they are genuinely exciting.

Three studies were recently published in the scientific journal Nature. Cell samples from 549 families were included. In each family, one child was autistic, but the parents and siblings were not.

Each study determined the sequence of every gene in every individual. Think of a gene as a string of pearls. Each "pearl" is one of four different nucleic acids, which are the building blocks of genes. The sequence of those nucleic acids determines what the effect of the gene will be.

Even 10 years ago such a study would have been impossibly expensive and taken hundreds of years to complete. However, new technologies now make it possible to sequence genes much faster, and for a tiny fraction of the cost.

All three research groups found very strong evidence that the autistic children had suffered serious mutations, or alterations, in at least three specific genes. The studies also found strong evidence of a role for another group of genes.

The mutations were not found in the parents or non-autistic siblings. So the mutations must have occurred in the DNA of the egg or the sperm that created the child with autism.

The studies also indicated that mutations in the father's genes (in the sperm) are more likely to lead to autism than mutations in the mother's genes (in the egg). Furthermore, mutations in the father's genes are more likely as the father gets older.

More important, virtually all of the genes that were mutated in the children with autism were genes that are important to brain development. So it made sense that mutations in these genes could lead to autism.

These new research studies are exciting. They sampled a relatively large number of families. And they all came to very similar conclusions -- which strongly suggests their findings are correct.

The studies do not identify "the cause" of autism. There are going to be many more genes involved. However, the identification of these genes will make it simpler to search for other genes related to autism.

Like most diseases, autism is likely caused not just by genes but also by factors in the environment. (My colleague Dr. Martha Herbert explains this in her wonderful new book, "The Autism Revolution." You can learn more about it at AskDoctorK.com.) Not every child in these studies with these gene mutations was autistic. It often takes environmental factors to reveal genetic vulnerability.

It will take time, but I think these studies will lead to improved diagnosis and treatment. It reminds me of what Winston Churchill said at the end of the Battle of Britain: "This is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning."

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.

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