Autisim

What is autism?

• Disorder of brain function that appears early in life -- before the age of 3
• Autism belongs to a family of related brain conditions affecting behavior early in life, which are often referred to as pervasive developmental disorder
• Cause of autism is unknown

Traits associated with autism

• social detachment, e.g., failure to smile at parents and an unawareness of events around them
• abnormal language development, such as repeating phrases in a mechanical voice
• unusual repetitive movements, e.g., rocking and flicking fingers
• mental retardation (usually in more severe cases)
• Traits vary in severity and persist into adulthood
• Some individuals with autism have amazing skills (e.g. Rainman)

Incidence

• Savant syndrome is quite rare (only about 200 cases ever recorded)
• childhood autism is more common, affecting about one in 700 children
• Boys are affected four times more often than girls

Can autism "run in families"?

• If a child has autism, each of the parent's later children has a 3% to 9% chance of having autism.
• This is 100 to 200 times greater than in the general population.
• Believed to be multifactorial inheritance
• Genetic component supported by twin studies

• The second study used the same twins, but changed the definition of autism
• new definition was looser -- people with milder behavioral problems were counted as autistic

Genes involved in autism

• no gene found yet
• Several candidate regions on chromosomes have been identified through linkage studies

Differential Diagnosis

(known genetic conditions that may share some symptoms of autism)

• Fragile X syndrome (the FMR1 gene on the X chromosome).
• Tuberous sclerosis (the TSC1 gene on chromosome 9).
• Duplications of part of the long arm of chromosome 15.
• Untreated phenylketonuria (the PAH gene on chromosome 12)

Environmental factors

• UNKNOWN
• Autism was thought to result from certain events before or shortly after birth
• Infection of the brain with herpes virus and infection of the pregnant mother with rubella virus
• Problems with brain structure are associated with autism, including hydrocephalus and, very rarely, a brain tumor
• 1993 British study was reviewed by both the Medical Research Council in Great Britain and the Centers for Disease Control in the United States
• The Centers for Disease Control concluded that: "to date there is no conclusive evidence that any vaccine can cause autism"

Web sites resources

• The autism page at the National Institute for Neurological Disorders and Stroke:

• The MedlinePlus web site for autism:
• The February 2000 issue of Scientific American has an article entitled "The Early Origins of Autism" (full text not on-line).
• More about autism from the National Immunization Program at the Centers for Disease Control:
• Diagnosis, assessment and interventions for Autistic Spectrum Disorders:

Notes

The information in this outline was last updated in 2002.