A group of researchers has identified a possible biological mechanism that might be responsible for a rare form of autism. In these cases, mutations of the BCKDK gene inactivates an enzyme that is necessary for breaking down certain types of amino acids. These essential amino acids cannot be created by the body and can only be absorbed from food.
It isn't clear exactly how the absence of these essential amino acids leads to autism however there is some limited data from mice and anecdotal data from parents that providing appropriate supplements can restore the normal level of these amino acids and lead to improvements in the symptoms of autism.
If all of that sounds a little confusing, think of it this way. A small genetic mutation prevents you from absorbing critical substances from your food and the long term lack of these substances causes autism.
If you are interested in more information about the subject, there is a good write up over on Questioning Answers, there is an article in Nature describing the finding, as well as the actual paper. There is also some details about what the the BCKDK gene does and prior links to autism here and here.
At the risk of sounding like a broken record, I think it is going to become increasingly clear over time that many, if not most, cases of autism are going to caused by a process like this. We are going to find that there are disruptions to critical biological processes that lead to the symptoms of autism and that by correcting these biological disruptions we will be able to help people recover from autism.
We are going to find that the behaviors of autism are a side effect (co-morbid, if you will) and that the real problem is the biological disruption and the damage that causes. So instead of the brain being wired "differently" because that it is written into the person's genes, it wired differently because some process is preventing it from developing normally.
However, as I said before, a critical part of a model like this is that recovery will be a two step process. Simply correcting the underlying disruption will not instantly remove the symptoms of autism. It will take time for the body to recover from the damaged caused and it will take time for old behaviors to be unlearned and new skills to be learned.
But the important part is that autism can be successfully treated. The key is going to be finding what the disruptions are in a specific person and finding a way of correcting those disruptions.