I have a son with Aspergers' (a milder form of PDD) who USED to have a lot of sensory issues to deal with. But there are therapies out there to deal with Sensory Processing Disorders. Occupational Therapists can help. For my son, it was crucial that we deal with the sound sensitivity, so he also had Berard Auditory Integration Training. He also had vision therapy supervised by an optometrist who is a Fellow of the College of Optometric Vision Development.
I can't say that any of these therapies were a cure-all. My son still has Asperger's and needs help developing social skills, but he is able to get through the day with much less stress and needs a lot less support than he would have otherwise. (His only modification is extra time for tests and he rarely sees his consultant teacher.) He can also enjoy activities that he would have totally avoided before--such as being a statistician for the high school basketball team. (He wouldn't have been able to tolerate going to a basketball game before, due to the overstimulation.)
I am totally frustrated that treatments that I have just described are so hard to get (you often have to pay for them out of your own pocket, like we did). Meanwhile, it's a lot more expensive for schools to pay for the additional support (special education teachers, speech services, 1:1 aides, etc.) but they do it anyway.