Autism and Genes

What are the chances that I will have an autistic son or daughter if my brother is autistic? This is a simple question, with no simple answer.  I venture to say this is a question on the mind of many siblings.

Today, I started looking at the scads of references to see if there is any consensus among scientists about whether autism is the result of a genetic disorder. In this short post, I cannot write an exhaustive review of the literature; I will try to provide a useful overview with references for those who wish to know more.

Complex subject

One of the reasons that this subject is so complex is that people with autism vary considerably, hence the overarching term Autism Spectrum Disorder (ASD). They range from poorly functioning people, like my brother, to very highly functioning people, like Professor Temple Grandin. However, according to Freitag CM, in a 2008 review paper, the majority of autistic disorders are genetic in origin;[1] the Autism Research Foundation concurs, stating, ” research strongly suggests that genetics play a significant role… “[2]

An autism gene?

Does it follow that if autism is genetic in origin, that there is an autism gene that is passed down from parent to children who don’t have autism? The consensus seems to be: no. Autism Today reports that “[i]n the majority of individuals with autism, there is as of yet not identifiable genetic cause.”[3] Autism risk could be related to mutations in a number of genes[4] or an accumulation of small genetic changes.[5]  The article at the Autism Today site[6] classifies autism as a disorder due to ‘complex inheritance’, meaning it is not passed to future generations in patterns as disorders which are predictable by the action of dominant, recessive or X-linked genes.

Great suggestion by Autism Today[7]

To get a better idea of autism risk, Autism Today suggests that the prospective parents consider whether genetic syndromes associated with autism can be ruled out. These syndromes include: Fragile X, tuberous sclerosis, abnormalities associated with chromosome 15, abnormality in a gene related to Rett syndrome; the Autism Society[8] adds congenital rubella syndrome, and untreated phenylketonuria (PKU) to this list.

If these syndromes can be ruled out, Autism Today suggests a more detailed family history be conducted by a genetic counselor familiar with autism so a rough estimate of recurrence of autism can be made.

At this point in time, there is no genetic testing for autism, but research is ongoing.

2 thoughts on “Autism and Genes

  1. I’ve only been involved in the autism community for a few years but you quickly begin to see some patterns – so yes, in most cases I would say there is a definite genetic link. As you say though, geneticists can not predict whether or not a proposed sibling of an autistic child or another close relative will also have autism – it’s pretty much a lottery, slightly decreased if the new child is female. However!!!! There is also what seems to be random or wild card possibility of a child with autism being born into a family where there are no relatives who have been recognised or diagnosed with having some form of autism. That’s my take on it! Totally anecdotal & unresearched 🙂

    • I agree. Although I just started reading up on the genetics behind autism, I believe that random mutations and cumulative chromosomal changes also contribute to autism risk. Also, some environmental conditions are risk factors as well.

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