Eosinophilic Granuloma Complex (EGC)
Eosinophilic granuloma complex, also known as eosinophilic plaques or rodent ulcers, are a hypersensitivity reaction, most commonly to allergens, that result in either a red scabby area on your cat's skin, or a swollen area on your cat's lips.
· Causes. These are most commonly caused by allergies, and rarely they can also be caused by bug bites or skin bacterial infection. When your cat is allergic to something, whether it is environmental, or something in their food, it can cause a systemic inflammatory response. In some cats, for reasons we don't know, the immune system over reacts to an allergen, and develops an area of intense swelling and itching from all of the eosinophils, which are white blood cells that respond by flooding into the area. On the skin, these are known as eosinophilic plaques, on the lips these are known as rodent ulcers.
· Symptoms. On your cat's skin, you will see a scabby area, which may be either rounded or linear, most commonly on the face, neck, or back legs, but it can appear anywhere. The scab will be very reddened, and you cat will be licking at it constantly because it itches so much. On your cat's lip, you will see a swollen area that may also look ulcerated.
· Treatment. The most effective treatment for EGC is steroids. The stronger the steroid, the faster the EGC goes away. However, while short term steroids are generally fairly safe, if we have to treat your cat with them regularly, then we run the risk of side effects, the primary one of which is the development of diabetes. We can also treat with other medications such as cyclosporine which is an immunosuppressant in conjunction with certain antibiotics, but these are more costly and not as effective as steroids.
· Prevention. Ideally, if we can determine what is triggering the EGC, then we can stop it at its source. Two ways to do this.
o Diet trial. To rule in or out a food allergy, we can put your cat on a hypo-allergenic diet for a few months to see if the EGC reoccurs. If it does not, then it was a food allergy, and your cat can be on the hypo-allergenic food for life. To be effective, this food needs to be fed exclusively, and generally needs to be a prescriptions hypo-allergenic diet made just for this purpose.
o Allergy test. This is pretty accurate for environmental allergies. This consists of drawing blood from your cat and sending it off to a Heska lab in Colorado that does nothing but allergy testing on dogs and cats. It takes a few weeks to get results, but they will look for antigens to various environmental allergies in your cat's blood, and send us back a list of what your cat is allergic to, and just how allergic they are. Once we know what your cat is allergic to, we can take steps to minimize your cat's exposure, or even start your cat on immunotherapy to desensitize your cat to the allergens. This is a somewhat costly test, but we have had very good results with it. However, there is a slight chance that we could do the test, and it could come back negative. This doesn't mean your cat doesn't have an allergy trigger, but the test didn't test for it. At that point we will start going through all potential allergens used in the home such as laundry detergent, etc., to try and determine the environmental trigger.
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This handout was written by Dr. Shelley Knudsen, DVM