Pemphigus Foliaceus (PF) is a non-contagious disease that affects the skin of dogs, cats, horses, and people. PF is both a disease of the immune system and the skin. The problem begins when the animal’s body recognizes parts of its own skin as foreign. As a result of this abnormal immune response, the skin is damaged. In a sense, the animal is trying to reject its own skin, just as it would try to reject a viral or bacterial infection. 

Why does the immune system recognize its own body as foreign? 
Various explanations have been proposed including genetic, environmental, drug, and viral factors. In dogs, there is evidence of a genetic component, as PF is seen most commonly in certain breeds. In particular, Akitas, Doberman Pinschers, Schipperkes, Dachshunds and Chow Chows may have a higher incidence of PF than other breeds. It is thought that there is a hereditary or genetic predisposition to develop PF, assuming that "other necessary ingredients" or confounding factors are present.

Clinical Findings

PF occurs in both males and females. The age of onset is variable and can be seen in dogs and cats less than one year of age or over ten years of age. Most cases start in mature adults. The skin lesions first start as small red spots that rapidly form a pustule (pimple) and then a crust. In most cases, the major lesions noted are the red spots and the thick crusts (scabs) that form over the spots. The crusts are most common on the nose, face, ears, and scrotum of male dogs, but can be found all over the body. Itchiness is variable, as some animals are not bothered at all, while others are constantly rubbing and scratching their skin. Some animals may develop secondary bacterial infections as a result of the damage to the skin caused by the disease or the rubbing.

Occasionally, the pet may also be depressed, lethargic, and not want to eat. During this time numerous areas of skin will develop crusts, almost as if a wave of crusting spread over the body. Rarely, these animals will also develop swelling of the legs and / or abdomen. Lameness from sore or stiff joints may be seen during flare-ups.

Diagnosis

The definitive diagnosis of PF should always be made prior to treatment as numerous, other, more common diseases can look like PF. A diagnosis via biopsy should be made so that the correct and appropriate treatment(s) can be started as soon as possible.

To diagnose PF, small pieces of skin will have to be surgically removed (biopsy) and sent to a lab where the diagnosis can be confirmed. Occasionally multiple biopsies may need to be taken to find one that will confirm the diagnosis. Site selection for the biopsy is very important.

Treatment

Once the diagnosis of PF has been made, then one of several treatment options can be considered. All options use different types of drugs that suppress the abnormal immune response - otherwise known as immunosuppressive drugs. Each drug has positive and negative effects. Rarely, serious side effects can occur, but frequent monitoring reduces chances of treatment complications. In most cases PF can be controlled so that the skin is kept normal with only rare flare-ups, however treatment is usually needed for life. Periodic monitoring will be required to watch for any side effects of the drug therapy.  

There is no test to determine what form of treatment the pet will best respond to. Several different drugs or combinations of drugs may need to be trialed to determine the best course of therapy for that pet. Some cases cannot be controlled with drugs currently available.

Contributed by:  Karen Helton-Rhodes, DVM, Diplomate ACVD