Swollen hock syndrome(shar pei fever) in a mastiff?

[Dr Meat]

Hi all, I am looking for a vet with experience of shar pai fever,or advice how to locate one.
Meet my boy Bronson

He is a 2yr old french mastiff cross that I have spent around 3k on trying to get to the bottom of he's health issues and hes currently on ten prednistlone(probably spelt wrong)tablets a day and tramadol tablets as and when he needs them.
Now for his health history and why I think he my have shar pei fever.
At 3 months old we had his hips x-rayed as he had a strange gate whilst walking every now and then(x-rays spot on)
At four months old he got a skin condition so at first we treated him for fleas,advorcate spot on and had the house fumigated to kill any fleas or dust mights.He then collapsed,mouth swelled up red ears & paws and had sickness &
diarrhea,he was rushed to emergency vets and treated for allergic reaction.The skin issue persisted we had skin scrapes done several times and blood tests for allergies,all tests clear! only steriods seem to help. 6mth strict diet trials and tried all anti-histamines with no effect we have even tried atopica ast a last resort with no effect.
He can go to bed fine then unable to stand in the morning,and i mean not even able to stay on his feet if we pick him up and every single time he cant stand he has a rageing temperature and is being sick and diarrhea.He has blackend areas on his skin that sometimes open up leaving small holes.he has very tender hocks, sore mouth.
His last collapse was about 2 weeks ago and they are getting more severe, he had x-rays again,blood & urine tests but all come back clear.He now spends most of the time laying down panting I can see he is in pain and I cant help him. When I asked the vet about swollen hock syndrome I was told that it was only found in shar pei's.If anyone has any suggestions I would be very greatful.