Section: Veterinary Care In-depth
Diagnosis In-depth
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.
Therapy In-depth
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.
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