What about Ehlers-Danlos Syndrome? Or any other connective tissue/ hyper mobile issues?
Another common one that I hear quite often, and have some personal connection to.
A few of my friends have this, or something similar, so I did help them get service pokemon and general help for it.
Pokemon who specialize in muscular precision, (Mienfoo, Medicham, even Lucario) are great for helping with the muscles and joints, usually knowing how to target specific areas for healthy stimulation.
The Goodra Line can help a lot with the skin issue, as the slime surrounding its body has healing properties with lots of minerals and moisturizing applications. So give a goodra a big ol hug.
A Pinurchin is actually really good for Acupuncture for the nerves as in low doses, their toxins combined with their electricity can help stimulate the nerves and joints to help them tighten up a bit.
A lot of this would be for different therapy, but having one or a couple of these pokemon as Service Partners wouldnt hurt at all.