Spotlight: Eosinophilic Granuloma

Eosinophilic Granuloma in Cats

Someone recently posted on Facebook that she was hoping her cat didn't have this condition based on a small lesion she'd found, so I thought it might be a good topic for an Old Maid Cat Lady blog post. It's been forever since I've written one, and this is as good a topic as any with which to resume.

What is Eosinophilic Granuloma Complex?

Basically, "EGC" is a skin inflammation that can look pretty scary. The term is used loosely to refer to different things, which can be confusing. Some vets also now refer to this complex as "feline eosinophilic diseases" which further adds to the confusion. More common names for the lesions are "rodent ulcer" or "lick ulcer".

There are three - possibly four - different syndromes that can cause the type of skin lesions commonly referred to as eosinophilic granuloma:

1. Eosinophilic plaque is typically found on a cat's abdomen, groin, or thigh area. These contain white blood cells known as eosinophils. They most often affect cats from ages 2-6 years, and are the itchiest form of the three.
2. Actual eosinophilic granulomas also contain eosinophils. These are also known as linear granulomas or collagenolytic granulomas. They are usually found on the face, in the mouth, or on back of the thighs. You may see these in cats who are genetically predisposed to get them when kittens, or before they turn 2 years old. Sometimes they will resolve on their own, without treatment.
3. Indolent ulcers are defined, ulcerated lesions most often found on the cat's upper lip. These are also known as rodent ulcer, about which I wrote another blog post last year. Be careful with these, as they may morph into a cancerous lesion.
4. Atypical eosinophilic dermatitis is the least common form. This one appears on areas of the body with the least hair, including the nose, ear tips, and footpads. Some veterinarians do not consider this to be a separate type of eosinophilic granuloma, grouping it with the #2 type above.

The first three types of lesions may develop simultaneously in your cat. Or you may see only one. As a complex, they are unique to felines. They are, however, rather uncommon. Additional forms can affect your cat's eyes and digestive tracts, although most vets still try to classify this condition based on the first three types listed above.

Because they're itchy, cats will often scratch, lick, or bite at these lesions. Once the skin is broken, this exposes them to other pathogens in the environment so that a secondary infection may occur. So they're not something you want to leave untreated.

What causes eosinophilic granuloma in cats?

Basically, allergies. As with all allergic reactions, it is an immune system disorder. Eosinophils are white blood cells that the body normally produces from bone marrow in response to contact with parasites and other bodily invaders.

Your cat may be allergic or hypersensitive to all types of things, from food additives to pollen, cleaning products...or even dust! When the cat's body senses the presence of these substances, the eosinophils think the body is being invaded by a parasite and release chemicals that cause inflammation (swelling) to kill the parasite. An overabundance of these in response to an otherwise benign substance causes the eosinophils to attack the collagen in the cat's skin and causes the lesions to erupt.

Some cats will develop these types of granulomas in response to a flea, mite, mosquito, or other insect bite. In multi-cat households, in fact, flea allergy dermatitis is often the first suspected cause. A secondary common parasite, cheyletiella mites - also known as "walking dandruff" - may be the culprits. Ringworm fungi and Demodex mites are others. The fourth type described above is always the result of an allergy to a mosquito bite.

Some cats have an allergic reaction to antibiotics or other types of medications. Airborne irritants like pollen or chemicals may also cause it: whereas we sneeze, our cats itch. Dust mites in your home, which are present year-round no matter how clean you keep your house, can also cause this type of allergy. If the lesions are seasonal, it's most likely pollen.

Some studies have indicated a significant genetic link to the tendency to develop these types of lesions. Most studies have shown that a cat's breed apparently has no connection to the condition. Another study showed increased risk among Himalayan cats. Females do show a slightly higher likelihood of developing the syndrome than do males, although this has not been greatly studied.

In some cases, no cause can ever be detected. Sometimes the lesions will resolve on their own, in which case it was probably a seasonal allergen that was undetected in testing. If your cat is going to get this condition, you will likely first see symptoms of it between ages 2-6 years.

What are the symptoms of eosinophilic granuloma in cats?

As varied as they are mysterious, the lesions associated with this condition may crop up suddenly or develop slowly over time. Your cat may scratch and lick them, or completely ignore them.

Often these lesions will appear as a rash around your cat's back legs or inside the mouth. They could be bumps or ulcers, and may be large or small. Most will be itchy, so your cat will most likely be scratching, licking, or biting at them.

The licking sometimes causes hair loss so that area around the lesions will be bald, making them easier to spot. If the hair hasn't all fallen out in that area, it will likely be wet and matted from the cat's frequent licking of the itchy spots. Licking and scratching also irritates the lesions, contributing further to the redness and swelling. You may notice swollen lymph nodes in the area.

Look for a defined, raised, yellow-pink lesion in the abdomen, thighs, or upper lip. These may appear ulcerated. Inside the mouth, on the face, or on the back of the cat's thighs, the lesions may appear more like a mass or nodule. You may find all three types at the same time, or just one or two types. Treatment for all three types is the same, so it really doesn't matter.

In the abdomen, thigh area, footpads, or near the cat's anus, the lesions will appear as very defined, yellowish-pink or white, raised, and round or oval in shape. They look something like hives, but are long and thin in a line where several of them have merged. Some have likened their appearance to a lightning bolt. It can also look like a cobblestone pattern. Quite often they will ulcerate, glistening like they're moist or even weeping fluid...if not ulcerated, they will look more like tumors or bumps. These may also appear under the kitty's front legs. You might see some hair loss and redness there, too.

The cat's lip or chin may swell from the eosinophilic granulomas. These may also merge like the ones on the backs of the thighs, and may cause pain that prevents your kitty from eating normally. There may be ulcers on the gums, palate, or upper lip. Sometimes they will bleed or cause the cat to drool. They can get quite large. When long-lasting, they may eventually grow concave and have a harder feel to them and cause the lymph nodes in the cat's neck to swell. If you find one on kitty's lip, check inside the mouth for more. These can cause permanent disfiguration.

Some older cats may get a smooth nodule that almost looks like a wart in the mouth or throat area. These can sometimes interfere with swallowing, or even breathing.

The indolent type (rodent ulcer) will not bleed and may not even cause any pain. They may appear on one side of your kitty's upper lip...or on both sides...or on the back of the tongue. And they may come and go.

Swelling may also happen on the footpads. This form seems to especially affect younger cats, under age 3. The nodules there will be raised, thickened and red. The footpads may crack. When this occurs, there will be some pain involved and you may notice some odor. Your kitty may favor the affected paws or appear lame when walking. Paws that are infected from injury will be warm and feverish, but that is not the case with EGC-inflamed paws.

Another very rare form of this condition can also affect the corneas of the eyes. This is known as eosinophilic karatitis. The clear cornea on the outer portion of the cat's eye will develop a raised, rough area that's amber-pink-gray in color. It does not respond to the usual treatments for eye injuries.

Although not all vets consider it to be a type of eosinophilic granuloma, there is another form of inflammation that can affect your cat's digestive tract. It may cause diarrhea, vomiting, and weight loss. All of these can also be symptoms of other digestive diseases, as well. A biopsy will reveal the difference.

In some cats, you'll see a recurrence of this condition throughout their lives. With others, they may have one incident and never have it again. Still others will never get it at all!

How is eosinophilic granuloma in cats treated?

Hope you've got your Sherlock Holmes deerstalker hat handy! The key to treating this condition is to eliminate the source allergen from your cat's environment. Before going to the vet, think carefully about whether anything new has been introduced to your cat's diet or your home that may have coincided with the onset of symptoms. Make a list of these.

Cats are highly affected emotionally by changes in their environment, so look at those stressors, as well. If someone in the family has recently moved in or out, you've remodeled, or have added a new pet to the household, this could trigger a reaction that looks like EGC.

If you've recently started feeding a new food or treat, stop feeding that for 6-10 weeks and see if the lesions disappear on their own. If they do, try re-introducing the new food to see if they reappear. If so, you have your culprit. The same goes for cat litter; if you've recently changed, go back to the old one and see if it gets rid of the lesions.

Have you started using a new type of laundry detergent or fabric softener? The cat may be sensitive to it. Plastic dishes can also cause reactions, as everything will get embedded in the tiny scratches of their surface. Switching to stainless steel or ceramic should help in those cases.

Have you recently started using a new type of household cleaner? Stop using it and see if the lesions go away, just as with the food trial. Has your cat been going outdoors in the evening during mosquito season? That could be the cause.

Have fleas infested your home or yard where the cat goes? This is probably the most common cause of EGC. Vacuum your house thoroughly, including using the edge cleaner to get all the way around the edges of rooms. Empty the bag immediately afterward. Use a flea comb and flip your cat over to look at the belly area; you may be surprised! There's your villains. If you use one of the spot-on flea treatments, the site of application may develop an irritation that looks like EGC. Check your cat(s) for ticks, as well. All cats in the home need to be treated, not just the one with the allergy.

Once you've tried the process of elimination and your kitty's still itchy, red and swollen, it's time to go to the vet. Remember that list of things you made earlier? Take the list with you, and note on it which things you tried removing and what the results of each were.

In addition to doing a complete physical exam, your vet may run blood work and a urinalysis to help diagnose the condition. The vet may also test your cat for FeLV and FIV, just as a precaution. These lesions look like a host of other, more serious, conditions, so it's important to do the right testing to get a proper diagnosis.

A biopsy may be taken if cancer is suspected. If the eye is affected, a test for FHV-1 (feline herpes) virus will also be given. Skin scrapings will most likely be taken for a histopathology and microscopic examination to check for bacteria, fungi, and other potential tiny causes. They will probably also take a smear of the lesions themselves because the eosinophils are quite distinctive when viewed under a microscope.

Some vets may do skin testing, where they inject highly diluted allergens just under your kitty's skin to see the reaction. Others do not find this helpful at all. It is similar to the allergy scratch-testing they do on humans. If the area injected gets red and swollen, the cat is allergic to that substance.

Veterinarians typically treat all three types of inflammation in this syndrome with corticosteroids, usually prednisolone or dexamethasone. These can be given by injection or with pills you administer orally. One to three injections over several weeks typically does the trick. A topical steroid spray can also be used with less side effects, although some cats will lick it off. Your cat should not have to remain in the hospital for this treatment unless it's a severe case that's causing significant pain.

Steroid treatment is not advised for a long-term solution, however; it will suppress your cat's immune system and lower kitty's resistance to diseases. They can also cause weight gain that can lead to diabetes, or even weaken your cat's heart muscle.

Some vets use antihistamines like chlorpheniramine, clemastine, or amitripryline in combination with fatty acids to treat eosinophilic granuloma. Their bitter taste may cause your cat to salivate a lot after you've given the pill, but this is nothing to be concerned about.

Some indolent ulcers may be frozen (cryosurgery) or removed with laser surgery while your cat is under anesthesia. If the transition to a cancerous form is suspected, they may be treated with radiation or chemotherapy using interferon, chlorambucil or cyclosporine (Atopica). Gold therapy (yes, using real gold) has even been used in rare cases to treat the inflammation! These drugs are also immunosuppressants, however, so should be used carefully and not for long periods of time. They are typically considered treatments of last resort, after all else has failed.

If a secondary infection has occurred, your kitty may also need treatment with antibiotics until the infection clears. Clavamox, Antirobe, or doxicycline given with food is often used for this. It will not clear the lesions, but will address the infection. Especially puzzling cases of EGC may require consultation with a board-certified veterinary dermatologist.

In the longer term, vets will treat these types of allergies with injections of tiny quantities of the allergens themselves, known as hyposensitization. These are just like the allergy shots people receive to desensitize us to allergens. If the allergen at fault is not one that can be removed from your cat's environment, this type of treatment may be the only long-term solution.

Probably the most important treatment is to identify the source of the allergy and remove that allergen from your cat's environment. Attacking the source of the problem should eliminate the need for giving your cats any medication and prevent recurrence.

What can I do to prevent eosinophilic granuloma in my cat?

Once you know the allergens responsible for causing these lesions in your cat, it's as simple as keeping them out of your cat's environment. 

Make sure to always feed your cat high-quality, meat-based foods. Cats are obligate carnivores, which means they must eat meat in order to survive. Meat is expensive, so lower-quality cat foods have a lot of grain fillers that can often cause allergic reactions in cats. Dry food (kibble) diets can carry food storage mites, so stick to a wet-food (canned, pouch, or raw) diet. Once you find a healthy food that your cat enjoys and that doesn't cause the lesions, stick with it. Cats don't need variety; they prefer consistency. If your cat is overly sensitive to any of the foods you try, there are some hypoallergenic foods available through your veterinarian. In some cats, a raw diet that removes all commercially prepared foods can do the trick.

Pay attention to the pollen reports for your area. If it's pollen season and your cat is allergic to a particular type, keep kitty indoors with the windows closed during that time. Sure, you'll get plenty of complaining, but that's preferable to an itchy attack of granulomas!

Use a cat-safe flea treatment in your home and yard, as well as on your cat(s). Treat all cats in the household, not just the one with the allergy. Also keep your cats indoors when biting insects like mosquitoes or flies are prevalent. If you have a screened area or "catio" those are great ways to let your cat go outdoors without fear of insect bites. Make sure you treat that area frequently for fleas, as rain can wash away previous flea treatments. Remember, mosquitoes can also spread heartworms, so it's best to keep your cat safe from them even without the allergy component.

Make sure the cleaning products you use in your home are safe for use around cats. But that's no guarantee, either. While "natural" may sound healthier, some cats can still have a sensitivity to a natural ingredient. If your cat is allergic to a substance in that cleaner, it's not one you want to use.

Our kitties are delicate creatures. We hate to see them suffer. And because these lesions are usually so itchy and awful looking, eosinophilic granuloma can be especially distressing! But with a little investigative work, trial and error, you can usually uncover the cause and solve the problem.

Sources: Skin Diseases from Allergies in Cats, PetMD.com; Eosinophilic Granuloma Complex, Cornell University College of Veterinary Medicine; Eosinophilic Disease in Cats, PetEducation.com; Feline Eosinophilic Granuloma Complex in Cats, VCA Animal Hospitals; Eosinophilic granuloma complex, International Cat Care; When Steroids Quit Working for Eosinophilic Granuloma, Veterinary News DVM360; Eosinophilic granuloma, Wikipedia; Eosinophilic Granuloma Complex, Veterinary Partner; Eosinophilic Granuloma Complex in Cats, Merck Veterinary Manual; What Is That Painful-Looking Red Wound on my Cat's Lip Or Body; 2nd Chance.

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