What if Autism Isn't a Neurodevelopmental Disorder?

Picture from Wikimedia Commons

Autism is typically thought of as a neurodevelopmental disorder.  It is assumed that something goes wrong early in a child's development and that the brain doesn't develop properly and that the result is permanent.

But what if that wasn't the case?

According to some recent research, the symptoms of Rett Syndrome (a form of autism) might caused by the continuing lack of the protein MeCP2 rather than problems with growth and development of the brain caused by the lack of MeCP2.  If that seems like splitting hairs, it really isn't.  That simple distinction means that Rett's might not be a neurodevelopmental disorder after all.

For those of you who don't know, Rett Syndrome is (currently) one of the five conditions that together make up what is known as the autism spectrum.  However, Rett's is somewhat different from other forms of autism.  It is rather rare (1 in 10,000) and effects girls almost exclusively.  It also tends to involve physical issues such as loss of motor control, severe digestive problems, and heart problems.  However, unlike other types of autism, a probable mechanism for the problems of Rett Syndrome has been identified - mutations in the methl-CpG-binding protein 2 (MeCP2) gene.

Because there is a known genetic mutation as well a known biological pathway that is disrupted, researchers have been able to create a number of different model of what Rett's looks like in mice.  Using these mice, researchers have been able to test a number of different theories about Rett's and this work has lead to a better understanding of the condition.

Early last year, researchers demonstrated, using mice that were deficient in MeCP2, that if you could restore the levels of MeCP2 in the brain that the mice's Rett-like symptoms would be reversed.  That part isn't too surprising but it does show that Rett's is an ongoing process.

What is more surprising is work done just this year.  This time researchers took mice that developed normally with the proper level of MeCP2 and removed their ability to produce this protein as an adult.  Once the protein was removed, these mice developed the same Rett-like symptoms as mice that were MeCP2 deficient their entire lives.

As a result, researchers are now shifting from thinking about Rett's as a condition that is caused by the lack of this protein during critical developmental periods (i.e. neurodevelopmental) and instead thinking about it as a life-long condition that is caused by the lack of this protein.

Or in other words, even though Rett's is "genetic", it is caused by an ongoing biological process and it should be possible to "cure" the condition by correcting this process.  So while there is not yet any cure for Rett's, the possibility of a cure for everyone with Rett's just got a little closer to reality.

What I find interesting is that Rett's isn't the only known "genetic" cause of autism that works like this.  In recent years Fragile-X, the leading genetic cause of intellectual disability and autism, has been shown to be reversible in adults and there are actually drugs in the works that might be able to do just that.

So what if other forms of autism aren't neurodevelopmental disorders either?  What if, like Rett's and Fragile X, other forms of autism are caused by an ongoing biological process rather than caused by something that went wrong during early development?  I think there is certainly enough evidence of ongoing biological disruptions in people with autism to make this a possibility.