Eosinophilic Granuloma Complex in Cats

By Malcolm Weir, DVM, MSc, MPH; Tammy Hunter, DVM; Ernest Ward, DVM

What is feline eosinophilic granuloma complex?

Eosinophilic granuloma complex is a term used to describe three forms of skin lesions in cats:

1. Eosinophilic plaque
2. Eosinophilic granuloma
3. Indolent ulcers

The exact cause of eosinophilic granuloma complex in cats is unknown. Some research studies suggest that, in most cases, a form of allergic response (hypersensitivity reaction) may be involved and is more likely in cases that are recurrent. Other studies suggest that the condition may at least be partially genetic or inherited.

What are the clinical signs of eosinophilic granuloma complex?

The most common site for these lesions is on the lips, especially the upper lip where they appear as ulcers. They are sometimes referred to as ’rodent ulcers’, although this term is technically incorrect. The lesions range from small and barely noticeable ulcers to large and extensive ulcers that disfigure the lips. Bleeding occurs from some lesions.

Eosinophilic granulomas may also develop in the mouth, especially along the gums and palate, or on other areas of the body. When lesions form in other locations, they usually appear as bald patches with raised areas of reddened skin rather than an ulcer. These lesions are often called eosinophilic plaques. Common sites are the hind legs and the stomach. The lesions can be large and may be itchy, as cats frequently lick and bite at the affected areas.

How is eosinophilic granuloma complex diagnosed?

Diagnosis starts with your cat's medical history and physical examination findings.

To obtain a definitive diagnosis, your veterinarian may perform a fine needle aspiration (FNA). FNA involves taking a small needle with a syringe and suctioning a sample of cells directly from the lesion and placing them on a microscope slide. A veterinary pathologist then examines the slide under a microscope.

A similar test is also sometimes performed by pressing a microscope slide against a suspected eosinophilic plaque. By examining the imprint under the microscope, numerous eosinophils (a type of white blood cell) may be visible.

In some cases, results from FNA may not be entirely clear and a biopsy may be necessary. A biopsy is the surgical excision of a piece of the lesion. The appearance of the characteristic lip ulcers is highly suggestive and a biopsy may not be required; however, if lesions are located elsewhere on the skin or in the mouth, a biopsy will rule out other diseases and conditions.

How is eosinophilic granuloma complex treated?

If an underlying cause is identified, treatment will be directed at removing this cause.

Flea and insect control is very important in the treatment of this condition. This is due to the suspected hypersensitivity reaction that causes it. Insect bites can trigger an exaggerated immune response in affected cats, causing or worsening clinical signs.

Some cats respond to elimination diet trials or hypoallergenic diets, suggesting an underlying food allergy as the cause. Most cats diagnosed with feline eosinophilic granuloma complex benefit from a hypoallergenic food trial (see handout “Food Allergies in Cats” for more information).

"Corticosteroids are the most common treatment to control the symptoms of eosinophilic granuloma complex."

Corticosteroids are the most common treatment to control the symptoms of eosinophilic granuloma complex. Corticosteroids are available in different forms that have different durations of activity; most often, cats are treated with corticosteroids, either in the form of oral tablets or long-lasting injections. Treatment may last for weeks or months because eosinophilic granulomas frequently recur and prolonged treatment will minimize the chance of recurrence. Side effects of corticosteroids are usually not significant in cats, but prolonged use can cause side effects such as an increase in weight.

Cyclosporine (Atopica®) is another drug often used in cats to manage allergic skin disease. It acts as an immunosuppressant and is a good alternative for cats that cannot take steroids.

What is the prognosis for a cat diagnosed with eosinophilic granuloma complex?

Most cases respond well to medical treatment and management. Since recurrence is common, life-long intermittent treatment is needed in many cases. Cats that are severely affected will require more aggressive treatment and a referral to a board-certified veterinary dermatologist may be beneficial.

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