The August 2011 issue of Archives of Neurology includes an article titled “Rett Syndrome: Exploring the Autism Link” by Alan Percy. Many readers of this blog will be familiar with Dr. Percy and his work on Rett syndrome, MECP2 duplication syndrome, and other MECP2 disorders. He is a Professor at the University of Alabama at Birmingham.
Percy provides a good summary of the various categories of disorders that have been linked to the MECP2 gene in one way or another, and also describes various genetic anomalies taht have been linked to autism. He goes on to point out distinctions between autism and Rett syndrome. Although he does not lay out similar distinctions between autism and MECP2 duplication syndrome, the comparison would be very similar to the one made for Rett syndrome and autism.
Percy is not the first to explore the connection between the MECP2 gene and autism. This blog posted a similar but much less technical discussion of the connection between the MECP2 gene and autism back in 2009 based on the work of Alicia Degano, Jeroen Pasterkamp, and Gabriele Ronnett at Johns-Hopkins.
Part of the challenge underlying all of these discussions is what is probably a false assumption underlying our understanding of autism. We have generally discussed autism as kind of syndrome and assumed that that it is a unified phenomenon with similar underlying processes. This is very likely a mistake, and may impede progress. Imagine if we assumed that headache was a syndrome and assumed that the same mechanisms applied to all cases. Some headaches are caused by blood clots or broken blood vessels, some are caused by stress and some by sore muscles. In the same way, autism may be a symptom of many different genetic and nongenetic causes.
In fact, there is a growing understanding that this is the case. For precisely this reason, the American Psychiatric Association has proposed redefining autism in a new way that is based entirely on behavior and does not exclude Rett syndrome, MECP2 duplication syndrome or any other specific syndrome. Under the new definition, if an individual exhibits autistic behavior, he or she is autistic. If the individuals autistic behavior is caused by a specific syndrome, it is simply identified as autistic disorder secondary to Rett syndrome, MECP2 duplication syndrome, or some other relevant syndrome. This new definition will shake up a lot of people’s thinking, but it is fundamentally more logical, will support more equitable access to programs, and most likely better research and understanding of the relationships between autism and genetic syndromes.