Q How does one manage eosinophilic granuloma complex in cats?
A Dr. Stephen D. White at the 28th World Congress of the World Small Animal Veterinary Association in Bangkok, Thailand, gave
a lecture on eosinophilic granuloma complex in cats and dogs. Some relevant points in this lecture are provided below.
The eosinophilic granuloma complex in the cat actually results in inflammatory reactions of the skin and can be associated
with hypersensitivity diseases. While this complex generally has been regarded as idiopathic, any underlying disease can result
in the complex. A recent article suggests that Felis domesticus allergen I (Feld I) could be an autoallergen responsible for chronic inflammatory reactions in cats with the complex. Cat
skin can respond with eosinophils to a diverse group of diseases, including allergies, pemphigus, neoplasia or pyoderma.
The lip ulcer (eosinophilic ulcer, indolent ulcer, rodent ulcer) is found usually on the upper lip of cats. Diagnosis is based
on clinical appearance and histopathologic examination, which generally reveals hyperplastic ulcerative superficial perivascular
dermatitis with eosinophils or neutrophils, mononuclear cells and fibrosis. Blood eosinophilia and tissue eosinophilia are
less common than the other diseases in this complex. The primary underlying diseases identified with the indolent lip ulcer
are flea allergy, food allergy and atopic dermatitis; when these are controlled, the lip lesion resolves.
The eosinophilic plaque usually is seen on the ventral abdomen or inner thigh. Typical lesions show raised erythematous orange
to yellow plaques. Biopsy reveals hyperplastic, superficial and deep perivascular dermatitis with eosinophilia, and at times
a diffuse, eosinophilic dermatitis. Eosinophilic microvesicles and microabscesses might be seen in the epidermis. The eosinophilic
plaque has been associated with the underlying diseases of food allergy, flea allergy and atopy.
Associated with mosquito bites
Feline eosinophilic granuloma occurs most commonly in the oral cavity or in a linear fashion on the back legs. A subset of
this disease has been associated with mosquito bites and presents as nodules, with or without ulceration, on the face, ears
and feet. This condition has also been seen on, or within, the chin of cats (feline chin edema) and affecting the foot pads.
Typically, the lesions have a papular to nodular configuration and histopathologically show granulomatous dermatitis with
multifocal areas of collagen coated with the released substances from degranulated eosinophils (formerly known as collagen
degeneration). Eosinophils are common in the biopsies from the face or oral cavity, and there can be a peripheral eosinophilia,
too. Eosinophilic granuloma of the hind legs has been associated with the underlying disease of flea allergy; it has also
been seen with an apparently genetic predilection in a colony of specific pathogen-free cats. Affecting the foot pads can
be associated with certain types of cat litter.
Definitive diagnosis of the eosinophilic granuloma complex should be made on histopathologic examination. If a primary cause
(allergy) can be determined and controlled, then lesions should resolve permanently unless the animal re-encounters the offending
allergen. Most lesions wax and wane with or without therapy; so an unpredictable schedule of recurrence should be anticipated.
Drug dosages should be tapered to the lowest possible level (or discontinued, if possible) once the lesions have resolved.
Traditionally, eosinophilic granuloma complex has been treated with intramuscular injections of methylprednisolone acetate
(Depo-Medrol) at 4 mg/kg, given once every two weeks for three injections. More-frequent use of this protocol will lead to
the development of diabetes mellitus in a high percentage of cats. If further corticosteroid treatment is needed, initially
oral prednisolone at a dosage of 1 mg/kg q12h, dexamethasone at 0.1-0.2 mg/kg q24-72h, or triamcinolone at 0.1-0.2 mg/kg q24-72h
may be used, then tapered to the lowest effective dosage.
In an attempt to avoid corticosteroids, the following treatments have been reported or used. In one study, four of four eosinophilic
granulomas, but zero of two eosinophilic plaques were shown to respond to administration of essential fatty acids (DermCaps).
Dosages approximated the manufacturer's guidelines. These are well-tolerated medications. Cyclosporine produced a good response
to a dose of 25 mg per cat in six cases of eosinophilic plaque and three cases of oral eosinophilic granuloma in one report.
In three cases of indolent lip ulcers, the response was less impressive.
Megestrol acetate at 2.5-5 mg every 2-7 days can be effective in rare cases and is not recommended because of the severity
of possible side effects.