A common observation is that people with autism seem to be sensitive to dairy products and to foods containing gluten – like bread and pasta. The sensitivities range from rashes to digestive problems to undesirable behaviors. There are two genes strongly implicated in gluten metabolism on chromosome 6 but they are not especially close to the only autism gene (so far) on that chromosome.
Likewise, there is a third gene, RMRP, at P13.3 on chromosome 9 but it is currently not close to anything involved in autism.
The only two genes known to cause lactase (the enzyme that breaks down the sugar lactose) defects are on chromosome 2 – not especially close to known autism genes either