Genetic abnormalities and autism

by Jennifer Bunn
Jennifer Bunn
Mar 27, 2012 in Neuroscience
Photo: iStockphoto

Abnormal early brain development and overgrowth due to an altered gene expression has been positively linked to autism. A study from Eric Courchesne and colleagues, published in PLoS Genetics, adds credence to the same author’s study published in 2011, which found a 67 per cent increase in brain cells in the portion of the brain (prefrontal cortex) that regulates cognitive development, communication and sociability.

The current study determined that the genetic expression that controls the number and development of brain cells in the prefrontal cortex is abnormal in autistic patients. This results in an abnormally high number of brain cells in the prefrontal cortex and (possibly) a lower number of brain cells elsewhere in the cortex. They researchers studied the brains of children aged 2 to 14, as well as those of adults with autism, and discovered that gene expression abnormalities do not remain static but change over the lifetime of the individual with autism. In other words, the changes in the brain that occur in children with autism are different from the changes detected in adults with autism. This study is important in that scientists may one day be able to target these genetic abnormalities, leading to new and novel prevention and treatment strategies.

What is autism?

Autism is a disorder which affects normal development and appears in the early years of life (generally before age three), affecting normal growth of social and communication skills.

What causes autism?

There have been several theories put forth regarding the development of autism. The most controversial of these was to do with vaccines. However, the research put forward was proven to be fraudulent after the author et al. manipulated the data to support their argument.* Some anti-vaccine advocates still believe there is a link between vaccinations and autism. At present, there is no qualifiable scientific evidence to link the two. Mercury poisoning, diet and abnormalities of the digestive tract have also been studied as possible causes of autism. There is a known genetic/hereditary component to autism. Abnormal brain chemistry/function is the leading area of study regarding the cause of autism. Studies such as the one above are pointing towards a genetic malfunction/altered gene expression as the most likely cause.

Who is affected?

Autism is more common in boys than in girls (approximately 3-4:1). The exact number of children affected by autism is unknown. Although it seems that autism is increasing, this is likely due to increased sensitivity in diagnosing the disorder.

What are the symptoms?

Symptoms may vary from moderate to severe and typically affect communication, response to sensory stimulation, social interaction with others, play and behaviour. Most parents are able to identify that something is wrong with their child by the age of two and seek help from their physician. In some, development is relatively normal until age one or two, at which point the child seems to regress- this is called the regressive form of autism.

Symptoms may include:

  • poor verbal/nonverbal communication
  • overly sensitive to touch, feel, taste, sound and sight
  • unable to handle changes in routine
  • repeated body movements
  • unusual attachment to objects
  • uses gestures instead of words
  • does not initiate conversation
  • slow development of language skills
  • withdrawn, does not make friends
  • lack of empathy
  • prefers to play alone
  • may not like physical contact
  • does not engage in imaginative play
  • short attention span
  • may be overly aggressive or passive
  • narrow interests

Diagnosis of autism

Autism is usually suspected first by parents, who may notice abnormal behaviour and bring it to the attention of their family doctor. There is no specific biological test for autism. Other condition must be ruled out, necessitating a thorough physical and neurological exam. Genetic and metabolic testing may be done. Screening tools for autism are available; however, children are best diagnosed by an expert in autism.

Treatment

Treatment is most successful when begun early. Occupational therapy, physical therapy and speech/language therapy may all be implemented. Medications such as risperidone, antidepressants and other mood stabilisers may be used to cope with tantrums, sleep disturbances, and aggressiveness. Applied behavioural analysis and therapy may also be integrated. Some children benefit from dietary changes, such as a gluten-free diet, although this is somewhat controversial.

References:

*In 1998, a controversial paper was published in the Lancet by Andrew Wakefield et al., which claimed to show a link between vaccinations and autism. The study was later proven to be fraudulent and the article was retracted by the journal. To read more about the Andrew Wakefield controversy and arguments around links between vaccinations and autism, follow the links below: 



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