Eosinophilic Granuloma Complex in Cats: an Itchy Mystery

Also called “rodent ulcer” and indolent ulcer, EGC is the medical term used to describe an inflammatory condition of cats’ skin. Eosinophils are a type of white blood cell that help fight off parasites and allergens. 

When a cat’s immune system perceives a threat, eosinophil cells are sent to the affected area for protection. Chemicals from these cells cause inflammation in the surrounding tissues. 

EGC is a sign of an immune system reaction. EGC is a sign of an immune system reaction. Buckley and Nuttall reported in the Journal of Feline Medicine and Surgery that most researchers agree allergic disease is the major cause of EGC in cats.

Many substances have been implicated including

• Plastic, metal, wool
• Bacteria
• Viruses
• Pollen
• Flea allergy
• Mosquito allergy
• Food ingredients

We don’t understand all the factors involved in this disease. Some experts believe genetic inheritance may play a role.

There is no pattern of increased risk for any age, sex or breed of cat. In other words, any cat can be affected.

EGC causes characteristic skin lesions but can sometimes be confused with other diseases. Typical EGC symptoms include:

• Hair loss
• Itching
• Pain
• Raised area of skin plaques
• Red skin
• Linear plaques on lips, feet, legs or trunk
• Scabbing or sores
• Orange or yellowish discoloration of lesions

Other diseases with similar-looking skin lesions include skin cancer, demodicosis, bacterial infection and fungal skin infections. Since it looks so similar to other diseases, it’s important to get an accurate diagnosis by testing rather than making assumptions! 

EGC is diagnosed based on finding eosinophils and other inflammatory cells in the skin lesions described by Bardargi, et. al. in the journal Veterinary Dermatology.

There are two main methods used to differentiate EGC from similar skin diseases. 

Cytology

A skin cytology test requires collecting a very small sample of cells from the affected area. One method uses a syringe with a small needle inserted into a skin plaque to suck up a few cells. A less invasive (and less accurate) method uses adhesive tape can also be used to pick up a few cells from the surface of the skin. The cells are then deposited onto a glass slide and examined microscopically for the presence of inflammatory cells, bacteria and yeast.

Biopsy

A biopsy collects a small piece of the affected skin tissue which is examined microscopically by a pathologist. This method is the most accurate test to diagnose EGC in cats but may require sedation or anesthesia. 

Treatment

EGC is an inflammatory disease with skin lesions that respond well to steroids. Your vet may recommend treating your cat for one to two weeks with oral prednisolone. Topical medication containing antibiotics and steroids can also be helpful.

Treatment of underlying hypersensitivities must also be considered. This may require

• Aggressive flea prevention on the cat and in the home
• Changing food and water dishes to glass or ceramic
• Hypoallergenic cat food diet
• Long-term treatment of allergies with cyclosporine

According to Cornell University veterinarians, EGC skin lesions often go away without any treatment at all. But your cat might suffer in discomfort for weeks or months.

It is possible to resolve the symptoms of EGC in most cases. However, if underlying causes are not addressed, you can expect your cat to have recurrences of EGC lesions.  

First, an accurate diagnosis is needed. Then you work with your vet to try various strategies to control EGC lesions. 

Ongoing anti-allergy therapy and flea prevention are often recommended to keep EGC lesions from coming back. 

You may consider doing a food allergy trial to see if this helps calm your cat’s skin symptoms. Ask your vet to prescribe hypoallergenic food to feed your cat for at least two months.

Finally, you should monitor your cat for the development of EGC lesions and intervene as soon as you see symptoms. 

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