Pemphigus is an autoimmune disorder in which the body’s own normal defenses inappropriately attack one of the layers of the skin. There are several subtypes of this disease, each of which involves a different layer of cells being damaged. Pemphigus foliaceus is the most common form diagnosed in dogs and cats. It is characterized by pustular crusty lesions that occur on the face, ears, feet, clawbeds, footpads, and often becomes generalized. Pruritus (itching) and pain are variable. Pemphigus most often occurs without warning or explanation; however, it can be a side effect of certain medications or a result of unchecked chronic skin disease.
Pemphigus can be masked by concurrent skin problems such as flea allergy dermatitis, mange, and atopy (inhalant allergies). Also, the lesions are very susceptible to secondary bacterial infection. They may improve with antibiotic therapy but will not resolve until the underlying disease is treated.
A skin biopsy must be performed in order to confirm Pemphigus foliaceus. A local anesthetic and mild sedative may be used, or a general anesthetic may be administered to obtain a more representative sample. The tissue is then analyzed by a pathologist who will confirm the disease and its subtype.
Pemphigus is treated with high dose corticosteroid therapy. Steroids suppress the immune system and stop the inappropriate attack on the skin cells. Because of the drugs’ suppressive effect on the entire immune system and the subsequent potential for side effects, confirmation of this disease with a skin biopsy is very important before beginning treatment. Side effects from high dose steroids include excessive thirst and urination, increased appetite and weight gain, panting, and iatrogenic adrenal gland suppression (medication-induced Cushing’s disease).
Alternative drug therapies for patients who cannot tolerate high dose steroids, or for those who do not respond to corticosteroids alone, include azathioprine, chlorambucil, or cyclosporine. Each of these medications suppresses the immune system and has side effects of its own. Blood counts may need to be monitored to check for bone marrow suppression. These medications can take several weeks to take full effect.
Pemphigus carries a fair to guarded prognosis. Some animals respond well to treatment, and some can take weeks or months before symptoms totally resolve. A lot depends on whether the medications are tolerated and side effects are manageable. Generally, patients are gradually tapered off of medication after the skin is completely healed.