Eosinophilic Granuloma Complex in Cats
This article will focus on a common inflammatory skin condition in cats known as eosinophilic granuloma complex (EGC).
Gee Doc, That’s a Mouthful...
Yes, but it's not as complex as it sounds. EGC is not a single disease, but it is a group of similar lesions that affect the skin, muco-cutaneous (mucus membrane-skin) junctions, and oral cavity of the cat.
Causes of EGC in Cats
The cause of feline EGC is unknown, but most cats affected by it have an underlying hypersensitivity or allergy. This may be a food allergy, atopy (inhalant allergy), or insect allergy (to fleas, flies). Sometimes, a seasonal pattern occurs and typically, signs of EGC wax and wane. Some evidence points to bacteria as a causative agent because antibiotic therapy dramatically improves the lesions or resolves them. There are three distinct types of lesions that are recognized. These are:
- Indolent or rodent ulcer
- Eosinophilic plaque
- Linear or eosinophilic granuloma
Two or three of these may occur at the same time. We'll discuss them each individually now.
Rodent Ulcer or Indolent Ulcer
Rodent ulcer is a red lesion with raised margins typically seen on the upper lip of the cat. It may involve the crease in the middle (philtrum), also. These lesions are ulcerated and crater-like. The lesions may occur on the lower lip as well. A cat's natural tendency to lick combined with its rough tongue may aggravate the condition. The cat owner will note varying degrees of swelling of the lip. The lesions may also extend into the oral cavity. As bad as these lesions or sores look, they are neither painful nor pruritic (itchy).
Eosinophilic Plaques
The eosinophilic plaque is a well-defined, raised, red, oozing, ulcerated lesion. While they can be found anywhere on the skin, the most common sites for these plaques are the abdomen, groin, and inner thighs. Plaques are considered a hypersensitivity reaction to fleas or mosquitoes. Unlike rodent ulcers, eosinophilic plaques are intensely pruritic (itchy), so cats affected by them may self-mutilate.
Eosinophilic Granuloma
Eosinophilic or linear granuloma is the third form of EGC. These lesions occur on the back of the thighs, the face, and the tongue and palate. The chin may become quite swollen, leading to a “pouty” appearance. Mouth lesions may lead to loss of appetite or drooling. Paw pads may become swollen. The lesions on the backs the thighs are usually mildly red, hairless, raised, firm and linear. They are not typically painful or pruritic. Lesions seen on the tongue or palate may have white on their surface if they have eroded or ulcerated. Cats with these oral lesions may have difficulty swallowing, since they can be painful. There may be a genetic propensity or hypersensitivity component to eosinophilic granuloma.
Conclusions on EGC in Cats
The key to treating these conditions is for your veterinarian to identify the underlying cause. If the primary underlying condition is allergy, treatment will generally involve administration of injectable or oral corticosteroids and removal of the irritant (flea etc) or a hypoallergenic food trial. Systemic antibiotic therapy can also be helpful. For lesions that no longer respond to corticosteroid therapy, other options include immune-modulating drugs, surgical excision, laser therapy, and radiation therapy. Omega-3 fatty acids have been shown to help in some cases.
If your cat is exhibiting any of these lesions, please consult your veterinarian. Because many other skin conditions have similar clinical signs, allergy testing may be recommended. Skin biopsies can help your veterinarian rule out skin cancer.
Prognosis is variable and depends on the underlying cause. If allergy is the primary cause and the allergy condition is managed well, then prognosis is good to excellent. If the primary underlying condition or cause cannot be identified, these cats typically require long-term treatment. Keep in mind that some of the previously mentioned treatments have side effects associated with long-term use. The treatment goal is to control lesions, not to cure them.
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