Autism

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Overview

What is autism?

Autism was first described by Leo Kanner in 1943 as "... an innate inability to form the usual biologically provided affective contact with people."

Autism is a severe neurodevelopmental disorder of unknown origin, which has profound consequences for affected individuals and their families. It is the most common of five disorders in the diagnostic category Pervasive Developmental Disorders (PDD) (ICD -10 Classification).The other four disorders are:

Pervasive Developmental Disorders are also referred to as Autism Spectrum Disorders (ASD). These five disorders are classically defined by a combination of qualitative impairments in three principal areas:

Autism varies widely in its clinical presentation, both within and between individuals. Developmental abnormalities are usually apparent before three years of age, and although the behavioural manifestations can change dramatically with development, the characteristic impairments persist into adulthood. Autism is often characterised by language delay and many individuals fail to develop any useful, meaningful speech, although they may have echolalic or stereotyped language.

Autistic children may dislike physical contact, making limited or inappropriate eye contact and interacting better with adults than with their peers. This may be demonstrated in later life by an inability to form relationships. Autistic children often show a lack of imagination or pretend play, and it has been suggested that autistic individuals lack a 'Theory of Mind' such that they are unable to understand or read body language and facial expressions, or the mental state of others.

Repetitive behaviours may include motor stereotypies such as hand flapping or body rocking, spinning of objects, parroted or echolalic speech, a fascination with simple sensory stimuli such as bright lights, and a dislike of interruption to daily routine.

Other features of autism in some individuals may include self-injurious behaviour, over sensitivity to some sounds or touch, sleep disturbances, odd posture and gait and a lack of motor co-ordination, a decreased affective response and lack of facial expression, hyperactivity and a poor general attention span, and gastrointestinal problems. Loss of skills, most frequently regression in language in the second year of life, affects approximately one third of individuals with autism, and although 90% of these individuals regain some skills, some may never achieve their previous level of functioning.

Mental retardation occurs in approximately two thirds of individuals with autism, and seizures develop in approximately one third. Those autistic individuals with mild to moderate learning difficulties may have higher or remarkable skill levels in some areas, particularly in visuospatial tasks, rote memory, mathematics, artistic drawing or musical performance.

The most recent estimate for the general population prevalence of narrowly-defined autism is approximately 20 in 10,000, with no apparent systematic geographic or socio-economic variation. The ratio of affected males to females is approximately 4:1.

However, recent reviews indicate that, when all the different PDD subtypes are combined, the prevalence rate may be as high as 60 in 10,000 children. There have been many recent reports suggesting that the incidence of autistic disorder has increased, although it is probable that this is partly due to improved recognition of the clinical variability of the disorder, and increased public and professional awareness.

Is autism genetic?

One recent estimate is that genetic factors may contribute about 90% to autism, while environmental factors contribute no more than 10%.

We have known for 30 years that genes usually strongly influence susceptibility to autism.

There is now convincing evidence from twin and family studies for the involvement of genetic factors in the development of autism. The absence of any strong consistent evidence for an environmental, biochemical or neuroanatomical cause has led to an increasing number of genetic studies worldwide to determine the basis of this complex disorder.

Several twin studies have clearly demonstrated substantially higher concordance rates in identical (monozygotic) twins, as compared to non-identical (dizygotic) twins. This implies a strong underlying genetic liability to autism.

A recent study indicates that the rate of ASDs in the siblings of autistic individuals is approximately 4% - a rate that is about 15 times the general population prevalence. This finding suggests that autism is one of the most strongly genetic of the childhood onset psychiatric disorders.

Twin and family studies have also suggested that this genetic predisposition extends to a broader autistic phenotype in the relatives of autistic individuals that includes a combination of milder, but similar, social and cognitive abnormalities in people of normal intelligence.

What are our goals?

Although scientists have long recognised the genetic component of autism susceptibility, it has only been technically feasible to identify which genes might be involved since the early 1990s. Because there were few clues about which genes might be relevant, or indeed on which chromosomes they might be located, it was necessary to scan all 23 pairs of chromosomes, a task that became possible only with the automation of gene discovery.

Professor Monaco's Research Group has been carrying out research on autism since the opening of the Centre. The Autism research team aims to track down the specific genes that are involved in autism. We are searching for the genetic variants that increase the risk of developing autism, using state-of-the-art technology to analyse thousands of genetic markers in large numbers of families with children affected by autism.

A main aim in identifying autism susceptibility genes is to enable the early diagnosis of autism, so that affected infants and their families can access the early intervention that is critical to obtaining the maximum benefit from existing therapies. In addition, it is hoped that identifying the genes involved in autism could in the longer term lead to the development of better medications, which could help improve the health and neurodevelopment of children with autism.

Recent publications

Pagnamenta A.T., Khan H., Walker S., Gerrelli D., Wing K., Bonaglia M.C., Giorda R., Berney T., Mani E., Molteni M., Pinto D., Le Couteur A., Hallmayer J., Sutcliffe J.S., Szatmari P., Paterson A.D., Scherer S.W., Vieland V.J., Monaco A.P. Rare familial 16q21 microdeletions under a linkage peak implicate cadherin 8 (CDH8) in susceptibility to autism and learning disability. Journal of Medical Genetics, Advanced Online. (2010) PMID: 20972252

Anney R., Klei L., Pinto D., Regan R., Conroy J., Magalhaes T.R., Correia C., Abrahams B.S., Sykes N., Pagnamenta A.T. et al.  A genomewide scan for common alleles affecting risk for autism. Hum Mol Genet, Advance Access 27 July (2010).  PMID: 20663923.

Pinto D., Pagnamenta A.T., Klei L., Anney R. et al. Functional impact of global rare copy number variation in autism spectrum disorders. Nature, 466, 368-372 (2010). PMID: 20531469.

Click here for a full list of recent publications.