Hi, I suspect I may have the same thing.
I've got severe sternum pain which seemed to start as the same time as pustules/psoriasis on my hands and feet.
My Doctor diagnosed excema (sorry about the spelling) which I was not sure about so I booked in to see a Dermatologist.
8 minutes and £130 later he diagnosed Psoriasis.
Unfortunately he was not a talkative chap and I didn't get to mention my sternum pain.
However, I have been doing some research on the net and I almost definately have this condition to.
The pain is now radiating from sternum to shoulder blade and has started to travel down my left arm. From what I can find out on the net an x ray does not always show the condition but an MRI certainly would as it would show up the inflammation around the joints.
There doesn't seem to be an awful lot of information regarding this and, what there is is mostly medical jargon.
I am really sorry to hear that you have had this for 7 years! Really hope that your Dr can get this sorted.
Out of interest, did your Dr say you may have it or did you look it up as well?
I am seriously considering going back to the Dr and telling him what I have found out about this. I read that it's a rare condition but some clinical studies have been done with various drugs and they seem to have worked.
I hope they have found a solution for you and, as you say, knowing the diagnosis is half the battle really, at least then you can deal with it!
Could you let me know the outcome of your investigations, I would be most interested.
Good luck