Welcome to disABILITIES! There are already several threads which cover similar questions which may be of assistance. Here is some basic information.
There is no such thing as a special PASS. At WDW (and now DL) there is a "Guest Assistance Card", usually referred to as a GAC on this forum. It is intended to allow people who have "invisible" disabilities to be treated as "normal". It appears this is what you are asking about.
At the first park you go to, you would have to go with the person to Guest Services. Having a name of disease/syndrome, or even a diagnosis, is not in itself sufficient. One thing it will normally not allow you to do is bypass lines. The GAC is good for the disabled individual and up to five members of the party, is good at all four parks, and valid through departure date.
Some of the things which mght be allowed in your situation would be to use a stroller as if it were a wheelchair (in lines), to wait out of the sun, or to have part of your group out of the line until just before the boarding area.
For many attractions they will suggest you use FastPass so you do not have long waits in line.