Eosinophilic granuloma complex (EGC) is a condition characterised by the presence of skin lesions over various parts of your cat’s body. It is thought to be due to a reaction to certain allergens such as flea bites, food or inhalant allergies.
An eosinophil is a type of white blood cell which participates in allergic reactions and helps to fight certain parasitic infections. A granuloma is an inflammatory lesion which contains granulocytes. These are a type of white blood cell made up of small cytotoxic granules, which are released (degranulation) in response to a microorganism or parasite.
The eosinophil’s job is to attack parasites. Once at the target location, it will release its granules to destroy the parasite.
Cats with eosinophilic granuloma complex suffer damage to local tissues due to biochemicals released by eosinophils in response to an allergic response.
Some cats may only experience a single episode, while others may have multiple outbreaks. There are three different types of lesion:
Indolent ulcer (eosinophilic ulcer or rodent ulcer): This affects cats of all breeds and ages, although it occurs three times as often in females as it is in males. Lesions typically develop on the upper lip (around the middle area), but can also be observed on the tongue. They appear as a raised, thickened red/brown ulcer which is well defined and glistening. Generally, while they may look so, they are not painful to the cat.
Eosinophilic plaque: The lesion can appear on any part of the body, but most often develops on the abdomen or thighs. They appear as red, well-defined, raised, hairless lesions which may be ulcerated.
Eosinophilic granuloma (linear granuloma or collagenolytic granuloma): This is more common in males than females, and cats under two years old. The back legs are the most common location. Lesions appear as long, straight, thin lines which are raised and inflamed, and pink in colour. Distribution on the face is seen as swellings and nodules on the bottom lip and the cat has a “fat chinned” pout. Footpads may also be affected by eosinophilic granuloma.
Your veterinarian will perform a physical examination of your cat, paying careful attention to the lesions. He will obtain a medical history from you including how long lesions have been present, other symptoms you may have noticed and any known allergies.
A tentative diagnosis may be made by visual examination of the ulcers. Your veterinarian may also decide to take biopsies of lesions for examination under a microscope.
Diagnostic tests to rule out other possible causes such as fungal cultures to rule out ringworm and bacterial cultures to check for skin infections will be necessary.
Skin prick test – A skin prick test is a test where multiple common allergens are pricked onto your cat’s skin, which is then evaluated 1-2 days later, if any of the pricks are raised and reddened, it can be indicative of an allergy to one (or more) of the allergens he was exposed to during the test.
Food trial – If your veterinarian suspects your cat has a food allergy, he will recommend a food trial. The cat is fed a novel protein, such as lamb, duck or kangaroo. During the trial, the cat must not receive any other food. If symptoms resolve, the cat will resume his normal diet to see if symptoms return.
If it is at all possible, identify the underlying cause and treat accordingly. This may include:
Ensure the cat is parasite free, treat regularly for fleas and worms.
Avoiding and or eliminating suspected allergens.
Flea control for cats with flea bite hypersensitivity which includes treating both the cat and the home.
Hypoallergenic diet for cats with food allergy.
Avoidance of the allergen for cats with inhalant allergy.
In addition to addressing the underlying causes outlined above, treatment of the lesions may include:
Steroids to reduce inflammation.
In severe cases, your veterinarian may prescribe immunosuppressive drugs such as Interferon.
Surgical excision or antibiotics for unresponsive lesions.