At the risk of starting a firestorm, I don't think there really is such a medical condition of "autism".
I have listened to so many parents in the community talk of their autistic children when it seems abundantly clear that their children act just like any rambunctious child. It seems that virtually any undesired behavioral issue in children is diagnosed as either ADHD or autism.
Look up "autism" in the dictionary: 1. (psychiatry) an abnormal absorption with the self; marked by communication disorders and short attention span and inability to treat others as people.
There's not a physical cause to this, but the doctors, nonetheless, pump millions of dollars in drugs into those individuals they have thus labeled.
What causes a child to have an "abnormal absorption of self", a "short attention span", and an "inability to treat others as people"? In the vast majority of cases, I submit that it is the way the children are raised--without God, by substitute parents in daycare, and indulged with every modern convenience and toy known to man. The fact that virtually 100% of American children are NOT diagnosed with autism is actually remarkable. For the most part, modern autism is a spiritual problem, not a psychiatric or medical problem. In fact, autism should be celebrated by modern liberals as complete success in instilling self-esteem.
Autism has just become, for the most part, another excuse for misbehavior and another "handicap" (I'm not even sure I'm allowed to use that word anymore) that must be accommodated by special preferences. In those very few cases in which autism is seemingly accurately diagnosed in babies, the doctors are either quacks or there really is something medically wrong but, not having any idea as to the cause or cure, the doctors simply slap on this new label which follows the child for life.
Thus, with true conversion, and very hard work that will likely continue to the very end of life, "autistic people" certainly are called by God to vocations.
I've read a few modern commentaries on some saints in which the modern authors claim that many were, in fact, "suffering" from autism, ADHD, and other psychiatric problems that would, today, be "resolved" with drugs. Somehow, the saints overcame their problems with prayer, fasting, and service to the Lord. I don't know any of them in which all that came easy, but that's why we recognize them as saints today--they overcame their problems in "getting along with people" by devoting their entire selves to others and to God.