Although published observations of autistic behavior date back to the 18th century it was not until 1943 that that disease was named (CDC). At that time Dr. Leo Kanner conducted a study of 11 children noting “autistic disturbances of affective contact”. The term autistic was coined about 30 years before to describe a condition marked by “a tendency to view life in terms of one’s own needs and desires”.(Random House Unabridged Dictionary) Around the same time Dr. Hans Asperger completed a study of 400 children noting similar behavior (CDC). The result was the classification of Autistic Spectrum Disorders (ASD) including autistic disorder, Asperger’s Syndrome, and pervasive developmental disorder-not otherwise specified. ASDs affect approximately 1 in 150 children in all races, ethnicities and socioeconomic groups equally (CDC, Beaudet, Maimburg, Cantor, Nagarajan). Autism is four times as likely to affect males as it is to affect females.
Autism is a developmental disability that is not related to intellectual capacity (CDC, Beaudet, Maimburg, Cantor, Nagarajan). Children affected with autism have difficulty with social interaction, communication, relating and understanding feelings and sensations, and paying attention. Autistic children may also have different ways of learning and may accomplish harder tasks, such as multiplication or reading words, before easier tasks such as number identification or letter pronunciation. Children with autism may be uncomfortable being touched and prefer solitude and undeviating routines and repetitive behaviors. A difficulty identifying appropriate feelings in a situation, personal space, body language and tone of voice are also symptoms common in ASDs. Verbal skills range from no language skills to relatively normal language skills although a person with an ASD may not recognize the natural ebb and flow of a conversation and stick to one personal topic for long periods of time. ASD symptoms are limited to social interaction and communication skills although they may be present along with another disorder such as mental retardation, epilepsy, Fragile X syndrome, tuberous sclerosis, congenital rubella syndrome or untreated phenylketonuria. Asperger’s syndrome is usually differentiated as a mild version of autism although the range of abilities and spectrum of symptoms in autistic disorder can be quite broad.
Since the symptoms for ASDs are so wide ranging it is important for infants and toddlers to complete standard screening tests (CDC). One-third to one-half of parents with autistic children notice symptoms by the child’s first birthday, with 80-90% noticing symptoms by the second birthday. The child may not have any difficulty with walking or other motor skills and show an ability to complete puzzles or other intellectual activities on par with their age group but they may not be able to play pretend or focus on objects or people. The child may also stop gaining skills or lose skills as a toddler. Early screening tests will help to identify those symptoms that may suggest autism (most children are diagnosed by age 4-5) in time to start behavioral therapies, currently the only treatment for ASDs. Some doctors may suggest talking to a nutritionist about diet changes that can help control symptoms and behavior. Similarly, some benefits have been seen with massage therapy, homeopathy, dance, or meditation. It is important to discuss alternative therapies with a doctor to prevent malnutrition or potentially harmful therapies. Currently, about one-third of autistic patients receive an alternative therapy although up to 10% may be harmful. Medication may also be given to control hyperactive energy levels, depression, seizures, attention deficiencies, or self-injurious behavior that frequently occur with autism or linked disorders.
ASDs are described as highly heritable although the genetic basis is unknown (CDC, Beaudet, Nagarajan). Simply put, a person with an autistic disorder may pass the condition to their child but may not have inherited the disease from a parent. De novo, or new, mutations occur in a number of genes that have been shown to be linked to autism (about 10-20% of cases). These mutations may be caused by environmental factors, although those are largely unknown. Another way of looking at ASD inheritance can be shown in twin studies. With identical twins, one twin affected with an ASD means the other has a 75% chance of being affected. A fraternal twin, however, has only a 3% chance of being affected if their twin is affected. Similarly, if a family has one child with an ASD there is a 2-8% chance of the second pregnancy producing a child with autism. Finding a genetic cause can be complicated. The cause may or may not be inherited. It may or may not be the result of a genetic mutation or environmental cause in the womb (thalidomide, for example). What other factors can contribute to ASDs if genetics and environment do not account for all the cases? Some cases can be explained by a different kind of change to DNA, what is called an epigenetic change. Genetic changes to DNA are considered changes to the sequence of DNA by deletion, duplication or base-pair change. Epigenetic changes to the DNA cover the way DNA is packaged in a cell’s nucleus. Each cell contains about 6 feet of DNA, clearly too much to fit in a cell without a highly-regulated packaging method (Hypertextbook). (Since every body has about 10 trillion cells the total DNA in every person can make about 70 trips to the sun and back). One method is called methylation and basically winds the DNA so tightly that the genes can not be expressed (CDC, Beaudet, Nagarajan). Methylation is common in cancer cells where most genes are hypomethylated, or turned on, while tumor suppressor genes (the brakes on tumor development) are hypermethylated. What this means for autism and other psychiatric disorders is that some genes the brain cells need for normal function are perfectly normal but locked away. One such gene can cause enough disruption to the brain to cause autism, schizophrenia or other psychiatric disorders. Altered methylation patterns have been linked to autistic patients with older fathers (Cantor) and some cases of assisted reproduction (such as IVF) (Maimburg); although, one study shows a decreased chance of autism after the rise of assisted reproduction. This study accounts for the cases where the assisted reproduction caused altered methylation. While it is not always known how methylation patterns in the brain cells are altered it is thought to occur early in development. Diagnostic tests are in development to identify these patients (Nagarajan). Likewise, drugs to undo methylation are in development and may be used to treat these subset of patients.
Not all cases of autism can be explained and no one explanation covers all cases. The broad range of symptoms and abilities in autistic patients is reflected in the many cellular causes of autism. Currently the best treatment for children with an ASD is an early diagnosis and behavioral intervention with medical treatment for those symptoms that require it.
Centers for Disease Control, http://www.cdc.gov/ncbddd/autism
Random House Unabridged Dictionary, Random House, Inc, 2006
Beaudet, Arthur L. Autism: highly heritable but not inherited. Nature Medicine. Vol. 13 No. 5, p. 534-6, 2007
Maimburg, Rikke D. and M. Vaeth. Do children born after assisted conception have less risk of developing infantile autism? European Society of Human Reproduction and Embryology. p.1-3, 2007
Cantor, RM. et al. Paternal age and autism are associated in a family-based sample. Molecular Psychiatry. Vol. 12. p. 419-423, 2007
Nagarajan, R.P. et al. Reduced MeCP2 expression is frequent in autism frontal cortex and correlates with aberrant MECP2 promoter methylation. Epigenetics. Vol. 1, No. 4, p. 172-182, 2006.
Hypertextbook, http://hypertextbook.com/facts/1998/StevenChen.shtml
