Well then, that is advanced chronic HLLE.....emperor angels do develop blotches when stressed or when they have Cryptocaryon or flukes, but those are mostly seen on the fish's flank, are smaller, more evenly sized, so that isn't it.
You can run a search and find a TON of discussions about HLLE here on RC. Skip the ideas about garlic, HUFA's, grounding probes and medications - none of those will work - the people who say they do are either mistaken, or they changed another parameter that was the actual cure. I hate to sound so dogmatic about this, but there is lots of junk information out there.
Changing the diet has been reported to work in some cases (Vitamin C supplements, higher amounts of roughage) - but this has never worked for me - in hundreds of attempts. Moving the fish to a different tank is almost always a component to seeing a cure. With that in mind, HLLE lesions that have been there for a year are not likely to ever go completely away.
I won't get into my own studies that implicate carbon dust as one important cause of HLLE, because if that was the cause, it is too late to do anything about it now....sorry!
JHemdal