Eosinophilic granuloma complex (EGC) is a condition characterised by the presence of skin lesions over various parts of your cat’s body.
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 that are triggered during an allergic response.
It is thought to be due to a reaction to certain allergens such as flea bites, food storage mite in dry food (T. putrescentiae), inhalant (atophy) allergy such as dust mites and pollen, and food allergies.
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, but can also be develop 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.
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.
- Avoid 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 although this is difficult with dust mites and pollen. Avoid the use of scented products in and around the home, don’t smoke inside.
In addition to addressing the underlying causes outlined above, treatment of the lesions may include:
- Steroids: To reduce inflammation.
- Immunosuppressive drugs: In severe cases, your veterinarian may prescribe immunosuppressive drugs such as Interferon.
- Zyrtec (cetirizine): A common over the counter antihistamine has anti-eosinophilic effects and can help in the treatment of eosinophilic granuloma complex.
- Surgical excision or antibiotics: For unresponsive lesions.