Autism is characterized by impaired social, communicative and behavioral development. It is a spectrum disorder, with symptoms and characteristics ranging from mild to severe. Common characteristics include resistance to change, a difficulty expressing needs, tantrums, difficulty socializing with others, an obsessive attachment to objects, over- or under-sensitivity to pain and a preference for being alone. There is no medical cure for autism.

Autism cannot be detected by medical tests; diagnoses are based primarily on observation. Its causes are unknown, though research indicates that genetics can be a factor, while many believe that environmental factors and even childhood vaccines may be to blame.

The Kirtons note all of these factors when questioned about the cause of their children's autism. They also point to John's age as a possible factor, as he was over 40 when all of his children were born. (Bobby, the oldest boy, is Robin Kirton's son from her first marriage.)

The Kirton's own research, through Internet searches, online discussion groups and local autism conferences, has led the family to believe it may lead the nation in the number of children with autism. It's a dubious distinction to John and Robin Kirton, but they also see it as an opportunity to educate others about the disorder and, maybe one day, start their own nonprofit organization to raise money for other families with autistic children.

This week, researchers from the Utah Registry of Autism and Developmental Disabilities, a joint project between the state health department and the U. medical school's department of psychiatry, will visit the family's home to draw blood from each family member as part of an ongoing study into the role of genetics in autism.

'Dangerous thoughts'

John and Robin Kirton bristle when asked the all-too-familiar question about their family: Why didn't they, as many parents do, stop having children?

Depending on their mood, the Kirtons respond with humor, frustration or defensiveness. Regardless, the answer remains the same — all of the Kirton children were already born when Bobby's fifth-grade teacher told John and Robin she suspected the boy suffered from Asperger's syndrome, a mild form of autism.

According to the Utah Registry of Autism and Developmental Disabilities, signs of autism-spectrum disorders are often the most obvious in 3 and 4 year olds, while more mild forms are often not diagnosed until later in childhood.

After observation tests confirmed Bobby, now 13, was a high-functioning autistic, the Kirtons began to become concerned about their other children. Sarah's diagnosis came next, then Ammon's.

"That's about when my grieving period started," John Kirton said.