Having a complex over eosinophilic granuloma complex? (Proceedings)

Eosinophilic granuloma complex is a dermatologic condition most commonly seen in cats. Allergies such as food allergy, atopy and insect hypersensitivities have been associated with this syndrome. If the allergic cause for this dermatitis is not found than the EGC is described as being idiopathic. No age or breed predilection exists. However, reports exist that suggest that female cats may be predisposed to developing EGC. Several clinical syndromes have been described for cats with EGC. These syndromes are: indolent ulcer (eosinophilic ulcer or rodent ulcer), eosinophilic plaque, eosinophilic granuloma. Each of these syndromes varies and they will be discussed separately.

Indolent ulcer

Indolent ulcer lesions have a distinctive appearance to them. Indolent ulcers are ulcerative lesions with a raised border. The most common location for rodent ulcers is the upper lip. Other areas where these skin lesions can be present are: oral cavity and other areas of the skin (possible but not as common). Pruritus and pain are rarely noted.

Differential diagnoses for indolent ulcers are infection (bacterial and/or fungal), trauma, neoplasia (ie SCC, cutaneous lymphosarcoma, mast cell tumor), and virally induce lesions (ie FeLV and/or FIV).

Eosinophlic plaque

Eosinophilic plaque is single or multiple plaques which are most commonly ulcerated. These types of EGC lesions are most commonly seen on the abdomen, medial thighs and other body locations (i.e. conjunctiva, cornea). Severe pruritus and peripheral lymphadenopathy are other clinical signs that can be seen with eosinophilic plaques.

The differential diagnoses for eosinophilic plaque are infection, trauma, neoplasia and virally induced lesions.

Eosinophilic granuloma

This syndrome appears as raised plaque lesions in a linear configuration. Erosion and ulcerations are possible. Eosinophilic granulomas are caudal thighs, face, and oral cavity. A peripheral lymphadenopathy is possible.

Differential diagnoses for EGC

Differential diagnoses for EGC are: infection (bacterial and/or fungal), trauma with or without a secondary infection, neoplasia (i.e. squamous cell carcinoma, cutaneous lymphoma, mast cell tumor), and virally induced lesions (i.e. FeLV and/or FIV) which may or may not be secondarily infected.

Diagnostic tests

Several diagnostic tests are useful for diagnosing and managing EGC. Skin scrapings are negative for ectoparasites. Skin cytologies and cultures usually show no evidence of infection. Complete blood counts may show peripheral eosinophilia (rare with indolent ulcers, common with eosinophilic granuloma and it is possible with eosinophlic granuloma. Serum chemistries and urinalysis are unremarkable. Food elimination and intradermal allergy testing may be positive. Histological lesions for the skin lesions vary. Indolent ulcers show a hyperplastic, ulcerated, superficial perivascular to interstitial dermatitis with neutrophils and mononuclear cells predominating. A fibrosing dermatitis is common. Rarely, a tissue eosinophilia is noted. For eosinophilic plaque lesions: a hyperplastic superficial and deep perivascular dermatitis with eosinophilia. Interstitial or diffuse dermatitis is possible. Flame figures may be seen. A diffuse spongiosis is commonly noted. Eosinophilic microvesicles or microabscesses are possible. For eosinophilic granulomas the histological lesions are a nodular to diffuse granulomatous dermatitis with multifocal areas of collagen degeneration. Eosinophils and multinucleated histiocytic giant cells (common). Flame figures are possible. Mucinosis of the epidermis and hair follicle outer root sheath commonly occurs. A focal eosinophilic folliculitis or furunculosis or panniculitis are possible. A palisading granumola may form around degenerating collagen. An eosinophilic infiltrate is less common with more chronic skin lesions.

Treatment

Several different treatment options exist for treating an ECG. Systemic steroids are most commonly used. The recommended dosage for prednisone or prednisolone for treating cats with ECG is 4.4 mg/kg q 24 hours PO then tapers to lowest every other day dosage. Side effects for prednisone and prednisolone include: polyuria, polydipsia, polyphagia, recurrent infections, hepatotoxicity, and iatrogenic Cushings just to name a few. Some cats are difficult to pill and methylprednisolone acetate (Depo-medrol®) is administered at a dosage of 10 to 20 mg SQ or IM per cat in place of the oral prednisone/prednisolone.

In difficult cases of feline ECG, some clinicians will use cyclosporine (Atopica®) has been used in place of systemic steroids. The dose of cyclosporine used is 25 mg per cat per day. One study used this treatment for 60 days to treat 12 cases of ECG. Nine out of twelve cats had an excellent response and 3 out of twelve cats had partial response. Relapse occurred at Day 90 in 2 out of the 12 cats. No side effects were reported but this study utilized a small number of cats and the study was not for extended periods of time. It is important to know that cyclosporine is not approved for use in cats. The owners need to be informed about this fact prior to prescribing these medications. This medication is only used for idiopathic cases.

If possible, the underlying allergy should be identified and controlled. If the cat has food allergies then avoidance of the offending food ingredient or ingredients is necessary to control the dermatological lesions. If the cat has atopic dermatitis then treatment options are: desensitization vaccines, antihistamines (especially chlorpheniramine) with or without a fatty acid supplement, steroids or cyclosporine. If the cat has flea allergy dermatitis then a medication for the pruritus as well as treating the pet and all the pets in the environment for fleas is important. Oral antibiotics and or antifungal medications may be necessary if a secondary infection is present.

Prognosis and outcome

The prognosis is favorable with appropriate treatment and management of the underlying allergy. However it is important to remember that feline ECG is a life- long management problem and this problem will never go away.

Selected Readings

Guaguere E, Prelaud P. Efficacy of cyclosporine in the treatment of 12 cases of eosinophilic granuloma complex. Vet Dermatol. 11:S31, 2000.

O'Dair H, et al. An open prospective investigation into aetiology in a group of cats with suspected allergic skin disease. Vet Dermatol 7:193, 1996.

Prost C. Diagnosis of feline allergic disease: A study of 90 cats. In: Kochka KW, et al (eds): Advances in Veterinary Dermatology III. Butterworth-Heinemann, Boston, 1998, p. 516.

Song, MD. Diagnosing and treating feline eosinophilic granuloma complex. Vet Med ;89:1141,1994.