A study published in the journal Nature Medicine has reported that in families with two children both diagnosed with autism, they are genetically similar only 30% of the time. Using whole-genome mapping techniques, siblings pairs were different 70% of the time — suggesting they had different “types” of autism. You can read about it in this New York Times article http://nyti.ms/1CIGyM4 and/or in this TIME piece: http://time.com/3683475/autism-siblings-study/
This has implications for treatment of course (e.g., using genome mapping with older siblings to diagnose and treat youngers), but also raises some interesting questions.
First, it calls into question the accuracy and utility of the autism diagnosis. The study’s authors argued that the difference was due to genetic diversity of the disorder. Perhaps it is that the diagnosis is not refined enough. It is too broad and accounts for too great a diversity of behaviors.
Second, there has long been a body of research on typically-developing siblings that shows they are more different than similar. These have focused on psychological and personality differences (not genetics), so a bit comparing apples and oranges, BUT the fact that siblings are more different than similar is no surprise to sibling researchers.
The question then becomes whether or not the same processes that support differences the same in all siblings — pairs diagnosed with autism and pairs who are typically developing.