Sjogren's Syndrome Support Group
Sjogren's syndrome is an autoimmune disorder in which immune cells attack and destroy the exocrine glands that produce tears and saliva. It also associated with rheumatic disorders such as rheumatoid arthritis, and it is rheumatoid factor positive in 90 percent of cases.

It never occurred to me there could be a link between my SJS, progressing edema, and odd transitory joint pains. Until one day it finally did. Some searching revealed it isn't uncommon for SJS patients to present with edema, not just of the feet but also trunk, arms, and even face, and joint pain (synovitis) of the knees, hips, etc.
Lungs showing up as hyper-expanded on an x ray indicating some degree of COPD isn't unusual either.
In SJS the autoimmune system basically attacks everything.
In one of the edema, synovitis presentations as above the patient was treated with Predisolone which I think is what they call Prednisone in England, and gradually recovered.
Odd though, since one of the posters below reported edema while on Prednisone and her physician attributed it to it.
Perhaps such things just flare up periodically then eventually disappear just as mysteriously until the next flare. I know they do for me. Sometimes I managed to forget I have SJS then *BAM* it hits me like a freight train. Every time the train is progressively larger than the last.
Be well.