Discovering the Genetics of Autism. (Medicine & Health)

Article excerpt

NOT TOO LONG AGO, the parents of a child who was diagnosed with autism were overwhelmed with disheartening information. They were told that their offspring might have to be institutionalized, that he or she would never be able to be a productive member of society, that nothing could be done to change this prognosis, and, worst of all, that they themselves were likely to blame for their child's condition. Doctors and scientists knew little about autism, and the lack of a clear diagnosis or any real understanding of its cause led to finger-pointing and misinformation.

Today, while autism is far from completely understood, the future for families of newly diagnosed youngsters is hopeful. Scientists have determined that autism is most likely caused by a combination of genetic and environmental risk factors. Poor parenting has been ruled out as a contributing factor.

Autism is a generic term that designates several more-specific disorders, known as pervasive developmental disorders, or PDDs. According to a website developed at Duke University's Center for Human Genetics, "Exploring Autism: A Look at the Genetics of Autism" (www.brilliantcontent.org/autism/), a child with PDD has a pattern of delayed or unique language development and impaired social interaction when compared to one without the disorder. Specifically, individuals with PDD show symptoms in three areas: socialization (interaction with others), communication, and repetitive behaviors. One of the most-difficult aspects of autism for family members is the struggle for emotional connection with the affected child. Those with autism have particular difficulty interpreting the variety of social cues people use to infer how another person thinks or feels. This may be part of a larger problem with generalization. Children with autism can often learn discrete tasks or follow specific sets of direction fairly easily, but characteristically do not apply what they learn to other circumstances.

Research into the causes of autism has taken off over the last few years. More resources are being directed towards understanding and treating it than ever before. However, understanding its causes is an enormously complex undertaking, as researchers who are attempting to identify the genes that may increase an individual's risk of developing autism can attest. Some of this complexity comes from the fact that autism is often difficult to diagnose. Nearly 60 years have passed since Leo Kanner first described autism as a distinct clinical entity in 1943, and the definition of the disorder continues to be refined.

What is known is that autism describes a set of neurodevelopmental problems which result in significant disturbances in social, communicative, and behavioral functioning. Autistic disorder and the other PDDs (Rett disorder, Asperger disorder, childhood disintegrative disorder, and PDD-not otherwise specified) are clinical diagnoses, which are made based on developmental history and behavioral observations. The onset is in early childhood, usually before the age of three, and symptoms persist throughout adult life. Scientists estimate that the best-known of the PDDs, autistic disorder, occurs in between two and 10 out of 10,000 children, which makes it almost as common as Down syndrome. In addition, male children are three to four times more likely to have autistic disorder than females. Having a clear description of the symptoms is the first step in identifying its genetic basis, because it allows researchers to define clearly autistic patients in the population. Once they are sure they can determine who has autism, scientists can begin the search for the specific genes involved.

Evidence that some forms of autism have a genetic basis was first published in the 1970s. Since then, data from multiple studies have confirmed this hypothesis. These reports included observational studies, such as case reports and observation of families with more than one autism patient, usually siblings. …