I recall reading that there is some connection with Psoriasis and the nastier forms of arthritis. The author of "The Singing Detective" spoke at length about it in the book and TV story. His knowledge of the subject was because he had a particularly agressive brand of both afflictions himself. He mentioned some major inroads in skin treatment that was a result of arthritis research.

Good luck MC I hope you get some help with the skin problem soon. By the way, have you had a thyroid function test done? There appears to be some connection there too.

Don