The general term eosinophilic granuloma complex (EGC) is one usually applied to cats although other animals, such as horses and dogs, can experience certain aspects of it. EGC represents an inflammatory skin condition, the symptoms of which may vary between species. The underlying cause is thought to be primarily hypersensitivity and allergy related involving the release of a type of white blood cell called eosinophils, although genetics (hereditary) probably play a role.
EGC refers not to one specific disease but rather a collective of several skin reactions or syndromes; namely eosinophilic granulomas (EG), plaques and indolent eosinophilic ulcers (some sources also include allergic military dermatitis e.g. Tilley & Smith 2011). Cats may exhibit any of the syndromes – each with their own characteristics regarding both appearance and location – but it is eosinophilic granuloma, uncommon in horses and rare in dogs, that is most frequently cited in canine literature.
Canine Eosinophilic Granuloma
When referring to species other than cats, some authorities deem eosinophilic granuloma to be a condition that, with regards to terminology, is not technically considered part of the ‘eosinophilic granulomas complex’. However, opinions differ concerning EGC terminology. For example, Bloom 2006 suggests the terms eosinophilic plaque, eosinophilic granuloma and indolent ulcer should be used for clinical dermatology but eosinophilic dermatoses for diagnostic dermatopathology.
Canine Eosinophilic Granuloma Causes
The precise cause of the condition is not clear at present; hypersensitivity is probably the primary factor though genetics appear involved e.g. possible inherited eosinophil dysfunction. Although it can affect any dog, it seems more prevalent in males (72% of cases) and in certain breeds such as Cavalier King Charles Spaniels, possibly German Shepherd dogs but particularly, Siberian Huskies (76% of dog cases ). The condition tends to appear earlier in breeds prone to the condition (below 2 years of age) as compared to other breeds (around 3 years of age).
Canine Eosinophilic Granuloma Symptoms
Eosinophilic granuloma symptoms in dogs tend to fall into 2 categories, namely:
| Category | Description |
| Oral Cavity Related |
Predominantly gender/breed specific, namely male Cavalier King Charles Spaniels (Bredal et al. 1996) and Siberian Huskies. One or more ulcerated lesions or vegetative masses typically on the upper sides of the tongue or the connecting soft palate tissues. Less common location may be the lips. Represents the most common form in dogs (Kim et al. 2011). |
| Cutaneous Related |
Not breed specific. Can affect the face, abdomen (ventral), flanks, prepuce and more commonly, the thighs (inner). Vercelli et al. 2006 documented a case of a Siberian Husky with an eyelid lesion. Often multiple papules, nodules and plaques. |
Related literature often describes canine EG as resembling feline EG (Kim et al. 2011). Descriptions of lesions include an appearance ranging from elevated, flat-topped and ulcerated with an orangey-red or darker coloration to red-yellow.
In both oral and cutaneous related cases, the frequency/severity can be unpredictable and can wax and wane over time with or without treatment. This factor coupled with location can give rise to other signs e.g. oral lesions may make it difficult for the dog to eat or drink.
Canine Eosinophilic Granuloma Diagnosis
Diagnosis will be based on a physical examination, taking into account the health history of the dog and possible skin, blood and other diagnostic tests. Part of the process will involve ruling out other conditions which exhibit similar symptoms e.g. various cancers. Histopathology – microscopic observation of eosinophils and associated inflammatory tissue – forms an important facet of diagnosing the condition (Kim et al. 2011). Therefore, histological samples involving smears and/or biopsy of the lesion should be taken.
Canine Eosinophilic Granuloma Treatment
Treatment of the condition includes preventative measures (avoiding probable allergens e.g. elimination trial for food allergies), symptomatic control (anti-inflammatories and oral steroids e.g. prednisone), immunotherapy (e.g. immunosuppressive drugs) and if persistent and unresponsive, surgical removal may be considered. Both radiotherapy and laser therapy have been used with varying degrees of success. Antimicrobials may also be utilized in order to prevent or indeed treat any associated infections.
