Overview of Pemphigus Foliaceus
Pemphigus foliaceus is a severe skin disease that is characterized by pustules and blisters that rupture, causing damage to the skin of the face, ears, feet and eventually the entire skin.
This disease results when the animal recognizes a specific component of his own skin (desmoglein I) as foreign and makes antibodies against that component. Desmoglein I is important in attaching skin cells to each other. Lack of this component causes the outer layer of the skin to split apart and fill with fluid and cells leading to a blister or pustule. This abnormality of the immune system is an example of an autoimmune disorder.
Middle aged to older cats are more prone to this disease. This disease has a severe health impact on the animal and can be fatal if not treated aggressively.
What to Watch For
Blisters and pustules that rupture and crust over beginning on the face and ears, and progress to the legs, feet, and eventually the entire body.
These animals may be very ill in advanced stages of the disease, and may refuse to eat.
Diagnosis of Pemphigus Foliaceus in Cats
This disease is confirmed by skin biopsy, preferably of an intact pustule. It is important that a pathologist skilled in reading veterinary skin histopathology read the biopsy.
Your veterinarian may puncture an intact pustule and collect the contents to put on a microscope slide for cytology (microscopic exam of the cells). This test may lead to a preliminary diagnosis that must be confirmed by biopsy. This test also helps to rule out other pustular skin diseases like pyoderma.
Treatment of Pemphigus Foliaceus in Cats
Immunosuppressive drugs. Since this disease is caused by an abnormality in the immune system, the immune system must be suppressed to treat the problem. Corticosteroids like prednisone are used at high doses for this reason. Although these drugs have the benefit of rapid suppression of the immune system, they have numerous side effects if used at this dosage long-term.
Once the disease is successfully in remission, other immunosuppressive drugs like azathioprine in cats may be used to help lower the dose of corticosteroids needed.
Chrysotherapy. Injections of gold salts have been successful as an aid in treatment.
Antibiotics. These may be needed if the skin is secondarily infected with bacteria.
Topical steroids. If diagnosed early in the disease course, topical steroids may provide temporary relief.
Home Care and Prevention
Give all medications as directed. Follow up appointments with your veterinarian are critical to allow for adjustment of drug dosages to maximize efficacy and minimize side effects.
There is no known way to prevent the development of this disease.
In-depth Information on Pemphigus Foliaceus in Cats
Pemphigus foliaceus is an autoimmune disease. In other words, it is caused by the animal’s own immune system. In this case, the body recognizes a glycoprotein, desmoglein I, found in the skin as foreign and mounts an antibody response against it. This glycoprotein is involved in the attachment of one skin cell to another within the outer layer of the skin (epidermis).
The result of the antibody binding to desmoglein I is a loss of attachment leading to a cleft within the epidermis. This cleft fills with fluid and white blood cells called neutrophils, which is the pustule that we see. Cells that are losing their ability to attach to one another round up and float into the middle of the fluid. These large, round cells are called acanthocytes. The pustules are very fragile and rupture easily leaving a lesion in the epidermis that is covered by a crust.
This disease tends to begin on the bridge of the nose and the ears and progress to the feet, including the footpads, and legs. Eventually the skin of the trunk and the rest of the body are affected. Often the lesions will cross from the skin on the bridge of the nose to the nose itself causing a loss of the normal cobblestone appearance and loss of pigmentation. Skin lesions that involve the nose are seen almost exclusively with autoimmune skin diseases. Animals with pemphigus foliaceus may have a fever and refuse to eat.
Other diseases that may be confused with pemphigus foliaceus are those that also have pustules as their major lesion. These include:
Pyoderma (bacterial infection of the skin)
Pemphigus erythematosus also begins on the head but fails to progress any further. Animals with pemphigus erythematosus are not usually as physically sick as those with pemphigus foliaceus.
Pemphigus vulgaris and pemphigus vegetans are also part of the pemphigus complex and are quite rare. The difference between the various pemphigus diseases is the depth of the ulcers. Pemphigus foliaceus has the most superficial ulcers. Pemphigus vulgaris has the deepest ulcers.
Discoid lupus erythematosus is an autoimmune disease that is often limited to the nose. Rarely, lesions may be seen on the ears, lips, and skin of the groin. This is a much less severe disease than pemphigus foliaceus.
Demodicosis, a skin problem caused by infestation with Demodex mites, often begins on the head and spreads to the legs and trunk. Secondary infection with bacteria can lead to pustules and make this disease look like pemphigus. There is no involvement of the nose with this disease.
Dermatophytosis (ringworm) is a fungal disease of the skin that can present as a pustular disease.
As with any skin disease, medical history and physical exam are important to the diagnosis. Expect to be asked where the lesions began and how they progressed. A complete physical exam with emphasis on the skin including exam of the nose and footpads will be done.
A skin scraping is often done to rule out infestation with Demodex mites.
A fungal culture may be done to rule out ringworm fungus.
A biopsy of one or more intact pustules is needed to confirm the diagnosis. Some cats will not have an intact pustule, but often one will appear if the cat is hospitalized and watched for a few hours. The pathologist will see a separation of the epidermis that has filled with neutrophils and larger rounded cells (acanthocytes). A lack of bacteria in the pustule helps to contrast this disease from pyoderma.
Specialized immune tests are available if the pathologist is unable to discern which autoimmune process is present in the biopsy (immunoflourescence and immunohistochemistry).
Cytology or the examination of the contents of a pustules can help give an early, tentative diagnosis of pemphigus foliaceus. Neutrophils, acanthocytes, and a lack of bacteria are also seen. Although the diagnosis should still be confirmed by biopsy, this tentative diagnosis may allow treatment to be started while waiting for biopsy results to come back.
Since autoimmune diseases are caused by an abnormal response by the immune system, the purpose of treatment of autoimmune disease is to modify the immune response. In the case of pemphigus foliaceus, drugs are used that suppress the immune response.
Corticosteroids such as prednisone are used in high doses to suppress the immune system and stop the antibody response to desmoglein I. The advantage of prednisone is that it works rapidly and animals with this disease often need rapid relief. The disadvantage of this drug is the potential for side effects when used at this dose. Side effects include increased thirst and urination, irritability, susceptibility to infection, adverse effects on the liver and adrenal glands, and muscle loss. Often corticosteroids are used early in the treatment and then other drugs that act more slowly and have fewer side effects are introduced to allow steroids to be decreased or eliminated. Other corticosteroids such as dexamethasone and triamcinolone may be tried if prednisone is ineffective.
Azathioprine is a medication that also suppresses the immune system. It is often used in cats to allow less corticosteroid use. Side effects of this drug are related to suppression of bone marrow causing decreases in red blood cells, white blood cells, and platelets. Thus, your veterinarian will recommend periodic CBC’s to monitor these cell lines.
Other immunosuppressive drugs are available if the above drugs are not effective.
Gold salt injections (chrysotherapy) have been used where other drugs have been ineffective or side effects have been unacceptable.
Early cases may be milder and respond to topical corticosteroids. These cases often eventually become more severe and require more aggressive treatment.
Home Care for a Cat with Pemphigus Foliaceus
Optimal treatment for your cat requires a combination of home and professional veterinary care. Follow–up can be critical, especially if your cat does not rapidly improve. Administer all prescribed medication as directed. Alert your veterinarian if you are experiencing problems treating your cat.
Medication adjustments are critical to management of pemphigus foliaceus and to avoidance of side effects. Thus, it is critical to keep recheck appointments.
Observe your cat carefully for response to treatment and for side effects and communicate closely with the veterinarian.
A periodic CBC will be done if immunosuppressive drugs like chlorambucil are used.