This topic was just covered in this month's issue of "Catnip" the magazine published by the Cummings School of Veterinary Medicine at Tufts University.
I will get my copy & post again later. However, from what I can recall from the article the standard treatment is steroids. Then reducing the steroids until the lesions appear again. This determines the least amount of steroids that will controll the disease.
http://www.tufts.edu/vet/publications/catnip/index.html