How old is this guy? Has a complete blood panel been run?? It would give you many more clues about whats going on with him...Please, let us know....Thanks
Do you mean PLE which can be found in the Yorkie breed, for one. If so, do a Google search and read up on it.
I don't know that much about other then I think a diet with less then 20 fat and low fibre is recommended. Some of the hypoallergenic foods may fit that bill. Sometimes, vitamin supplements and diuretics are needed.
Sorry, I am unable to give much more advice but hope you can find some answers.