"Pemphigus" is Greek for the word bubble or blister. This term is used to describe a group of uncommon but potentially life-threatening autoimmune skin diseases that develop on the skin and mucous membranes. In these diseases, an abnormal immune response causes the body to attack elements of the skin, damaging it. The diseases are relatively rare, and they are often mistaken for other disease processes like bacterial and fungal dermatitis.

Pemphigus Foliaceus is the most common of these disorders in horses and the least aggressive. PF causes circular areas of skin blistering, scaling and crusting. The lesions usually first appear around the face and limbs and gradually spread over the rest of the body. Affected horses are often depressed and lose weight and may have low-grade fever. Areas of ulceration can be painful and may ooze fluid, but are rarely very itchy (pruritic).

Diagnosis requires skin biopsy that usually shows characteristic microscopic changes. Treatment is long-term immunosuppressive drugs, including steroids. While these drugs may cause remission of signs for a time, signs usually recur.