I have no actual experience with this “disease”, so everything I know comes from anecdotal evidence obtained online. Probably the best description of Tang Fingerprint Disease comes from this trusted source: http://chucksaddiction.thefishestate.net/disease.html
Tang Fingerprint Disease. Oval fingerprint-like areas of discoloration occur on the sides of tangs and surgeon fish. Fish feed well at first but deaths can occur. Given ideal conditions the disease appears to be self-limiting. Initially thought to be a result of traumatic damage, microscopic investigations failed to confirm this; it is believed to be viral although no viral particles have yet to be identified.
This Kole Tang had this discoloration (similar pattern) on both sides of his body. None of the other fish/tangs were affected, and it seems unlikely that a coral or anemone sting would have caused similar looking markings on both sides of the body.
The next morning the fish appeared to be perfectly fine. The discoloration was gone, like it was never there. No antibiotics or other medications were ever used.