Fingernail Psoriasis but nowhere else?

Is it possible to have severe fingernail psoriasis (8/10 nails are falling off and have been in this state for 9 years) without having it anywhere else?

They've tested for fungus and say it's not that. My nailbeds are so damaged that I'm afraid I'll never get this cleared up. They hurt like crazy sometimes and especially if I hit them on anything. They're nearly all detached, and sometimes they move over to the side of the top of my finger when they grow. I have "bubbles" under most of my nails as well, because the nailbed is all hooved up in the middle.

None have ever come completely off, but I now have one fingernail that's completely detached and I clipped it clear back to the quick and the only place it's attached is where the lunula would be if I had any.

Is there anything I can try to get rid of this? They've suggested MTX, but no one's willing to go that route, even though I've had this for nearly 10 years. I have no other areas of psoriasis anywhere.

Thanks! I have had CRPS (RSD) or so they think, for 13 years. I may also have chronic vasculitis, but definitely no skin psoriasis.

I haven't been treated for it, other than topical steroids and antifungal medications. It seems like such a small thing to have something ailing with your fingernails, but when you consider that everything you do with your hands requires fingertips, and when those fingertips are painful and throbbing, and then when your nails are missing, it makes it impossible to grasp things, scratch, wash your hair without pain, anything that requires grasping. It's definitely not the end of the world, but it would be nice to have it resolved, or at least to know what's causing it.