PANS-mom

I think you should look into Lyme disease and all coinfections. If your family members were all exposed to the same environment, and having the same genetic makeup, it would only make sense that same problem is expressing itself, if somewhat differently.
 
Read the book "Cure Unknown" by Pamela Weintraub . Great source of Lyme information. BTW do you live or vacation in a Lyme endemic area?

I know of a couple families in my area where both or all 3 kids have PANS or PANDAS. I think that the number of families that there are like this is a very strong indication that there is a genetic susceptibility. That is not surprising for an autoimmune disorder.

27?!  That makes me with my onset at 13 feel quite mainstream.  I've been told occasionally that it can't be PANS at that age.  Well, somuch for that, evidently. 
I think there is supposed to be a reason for it in that it's supposed to be a thing that happens when the immune system isn't fully developed yet, but perhaps yo u and I just have something odd about our immune systems.  I mean, genetics can get you in all kinds of ways, so maybe we have some kind of as-yet-undiscovered genetic problem with our immune system that meant that whatever it was that's supposed to have happened by then that makes you no longer susceptible to PANS reactions, hadn't.  Just speculation. 
(It's also, I think, true that neurological Lyme disease is mostly not even about immune reacions but to do with the bacteris directly nib bling at neuron insulation, so presumably thed developed-immune-system thing wouldn't apply.)
(I am literally like a house with mice chewing the wiring.  :-)  )

My son has been on Zithromax for over a year (500mg 3x a week) and his Dr. wants him to be on it until he has and adult immune system. We have discovered that when he goes off the antibiotics, he starts to relapse.