Wow. Looks like a serious case of Tuberculosis to me.
Unfortanetly, I would say your fish is quite gone at this point in the cycle.
Here is a website with info about TB, but you might want to consider euthanizing this fish, and then agressively treating the rest of your tank with anti-bacterial meds.
And a site devoted to euthanasia:
Might want to wait for a second opinion, as this is just my advice. I have never seen or heard of a fish coming out of a TB infection that looks like that... nor treated a TB infection. Treat the rest of your tank agressively, and if you have the means to...take the fish from the infected tank out, and boil the things inside of it and start over from scratch.
Sorry to tell you.
Live in the Western MD/West Virginia/DC Metro Area?
Join our very active regional forum Here
Like the advice someone just gave you? Add to their reputation! Click on the balance icon underneath their username and let them know.