Don't worry, there wouldn't be a connection with your husband's MS. But there COULD be a connection with the Pervasive Developmental Disorder (PDD). If he has hypermobile joints, which seems to happen with some kids with Pervasive Developmental Disorder (PDD), this could cause pain in larger joints especially, as well as extremity joints. How is he with holding/using a pencil? Will he happily scribble away or does he stop fairly soon? Does he complain of pain? What is his grip like?
Hypermobile joints could also cause (commonly) pain with writing tasks (later on) and difficulty with writing to the point where he could have to use a keyboard instead for schoolwork. From what I've seen - this seems to happen with a lot of hyperlexia cases as well as other high-functioning autistics and Aspies. It's bizarre to see a physical symptom like this for a neurological condition like Pervasive Developmental Disorder (PDD).
I recommend running ALL these possibilities past the doctor, see what they say. Maybe get an Occupational Therapist (OT) to check it out especially if you have to see one for something else. We still haven't got difficult child 3 to a rheumatologist although I think we need to sooner rather than later. I've found out about ring splints, they can help with hand issues although it's a bit late for difficult child 3. He's found his own ways of coping, including use of keyboard. He's a fast typist.
I hope you can get some answers.
As for why a bandaid makes it better - I suspect it's because he is less anxious therefore less tense and this could also be reducing his pain.
Marg