Pet Autoimmune Disease
What are autoimmune skin disease and pemphigus foliaceus (PF)?
Autoimmune skin disease is a condition in which the body's immune system targets the skin for destruction. The damage results in lesions that normally can be seen by careful examination of the skin. Pemphigus foliaceus (PF) is a type of autoimmune skin disorder. With this disease, antibodies produced by the immune system combine with the action of white blood cells to damage the "glue" that holds epidermal (skin) cells together.
What makes the immune system attack the skin?
The inciting factor that results in the malfunction of the immune system is usually not known. One theory is that the skin is somehow altered, making it appear "foreign" to the immune system. Since one of the immune system's normal functions is to remove foreign substances from the body, the immune system attacks the altered skin. In the case of PF, the immune system produces antibodies against the "glue" that normally keeps skin cells (keratinocytes) attached to one another. White blood cells move in causing further damage, and the keratinocytes break apart from each other, forming visible lesions that look either like pustules (pimples) or crusts (scabs).
What types of things change the skin, making it appear foreign to the immune system?
Again, the inciting factor in most autoimmune diseases is not known with certainty. Damage to keratinocytes by viruses, bacterial infections, sunlight, or injury may damage and/or alter the skin and therefore play a role in initiating autoimmune skin disease. There is likely some genetic susceptibility in some dogs. Additionally, certain drugs can attach themselves to skin cells in such a way as to make the keratinocytes appear foreign. Drug-induced pemphigus does occur in dogs and cats, and for this reason, veterinary dermatologists always want to know what medications an animal with pemphigus had been receiving any time during the weeks before the onset of the disease. However, the majority of cases of canine and feline pemphigus foliaceus are not drug-induced and the inciting cause is not determined, as is the case with the disease in humans.