Pemphigus covers a group of uncommon disorders that occur in dogs. With these conditions, there is an abnormal immune response to normal components of the skin, resulting in separation of cells. This leads to blisters, pustules, and crusting erosions in the skin. There are some similarities to pemphigus in humans, but many significant differences as well.
Breed predispositions are recognized for 2 forms - pemphigus foliaceus and the milder pemphigus erythematosus. (There are no breed predispositions recognized for the other 2 forms - p. vulgaris and p. vegetans).
Pemphigus foliaceus and erythematosus develop around 4 years of age. P. erythematosus is thought to be a milder form of p. foliaceus. Both conditions begin with pustular, crusty lesions on the face and ears. However with p. foliaceus, the lesions spread to the feet, the groin and other areas; there may be itching and pain; and severely affected dogs may lose their appetite and become depressed.
Loss of pigment in the nose is common with both forms of pemphigus, and this results in photodermatitis - increased sensitivity to the sun's rays so that the condition is worse in sunny weather.
P. foliaceus is the most commonly seen form of pemphigus; however it is still uncommon. Your veterinarian will base the diagnosis on your history of how the condition developed, physical examination of your dog, and tests such as skin scrapings and smears, skin biopsy, and immune testing to rule out other causes of similar skin lesions such as a bacterial or fungal skin infection, mites, seborrhea, dermatomyositis, and lupus erythematosus.
Treatment is based on suppressing the inappropriate immune response. For pemphigus foliaceus, steroids (as a cream, or orally as a tablet - prednisone) are used to accomplish this. Once the condition is under control, your veterinarian will reduce the dosage to every second day to avoid the side effects which can occur with these drugs. Long term treatment is generally necessary. Where prednisone is not effective (as is sometimes the case), your veterinarian will try other immunomodulating drugs or chrysotherapy (gold salts).
For dogs that have lost pigment in the nose, protection against the sun is important to prevent flare-ups of the condition. Keep your dog out of the sun between 10:00 and 3:00 and/or use suncreens on the nose with SPF of 15 or higher.
The milder form, pemphigus erythematosus, may be successfully treated with sun avoidance and glucocorticoids applied to the skin. If this is ineffective, oral glucocorticoids or other drugs may be required.
For the veterinarian: A combination of tetracycline and niacinamide has been used with some success in dogs with p. erythematosus (Scott, 1995 below).
Multiple skin biopsies will increase the chances of finding diagnostic histologic changes. Direct immunofluorescence or immunohistochemical testing may or may not be helpful. These tests have relatively low sensitivity and specificity.
It is advisable not to use affected dogs in breeding programmes, even though inheritance for these conditions has not been worked out.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Scott, D.W., Miller, W.H., Griffin, C.E. 1995. Immunologic Skin Diseases. In Muller and Kirk's Small Animal Dermatology. p. 500-518. W.B. Saunders Co., Toronto.