Feline eosinophilic plaque

36 Feline eosinophilic plaque




INITIAL PRESENTATION


Eroded raised plaques in a domestic short-haired cat with eosinophilic plaque.



INTRODUCTION


Eosinophilic granuloma complex represents a reaction pattern often seen in cats mostly with an allergic or ectoparasitic aetiology.


Eosinophilic granuloma complex includes three different entities – eosinophilic granuloma, indolent ulcer and eosinophilic plaque – which, although they have distinct clinical appearances, may have common aetiologies. It is not unusual to see more than one syndrome on the same animal, either at the same time or sequentially. In a small number of cases, cytological examination and a good response to antibacterial therapy confirms bacterial involvement.




CASE PRESENTING SIGNS


A 5-year-old, spayed domestic short-haired cat was presented with multiple raised plaques, with eroded, ulcerated and exudative surfaces on the medial aspect of the thigh.



CASE HISTORY


Given that eosinophilic granuloma complex is a reaction pattern rather than a diagnosis, a detailed history is invaluable in helping to determine the underlying cause. It is important, therefore, to take a full history, which includes the signalment, age of onset, management and any previous treatments.


In this case the relevant history was:


• The first sign of disease was 2 years previously and consisted of pruritic lesions over the groin and medial thighs. These lesions resolved with a single injection of a depot glucocorticoid, methylprednisolone acetate.

• Since then there had been further similar episodes, which also responded to depot glucocorticoid injections. However, the most recent episode had failed to respond despite multiple injections given at a higher dosage.

• The cat was polyphagic and polydipsic.

• The diet consisted of a variety of commercial foods.

• The cat received routine thorough flea control consisting of monthly applications of fipronil spot-on and the house environment had also been treated with a permethrin and pyriproxyfen spray twice in the last 3 months.

• There were no other animals in the household and the cat was allowed out during the day.

• There was no reported zoonosis.


CLINICAL EXAMINATION


In cats with eosinophilic plaque, the lesions are usually located on the ventral abdomen and medial aspects of the thighs. They appear as circular raised, eroded or ulcerated plaques, ranging from 1 to 2 cm in diameter, but they may coalesce into a large lesion several centimetres in length. Uncommonly, lesions may appear on the feet, which usually present with crusting, exudation, erythema and swelling of the plantar or the interdigital skin (Fig. 36.1).


image

Figure 36.1 Erythema, crusting, exudation and swelling on the plantar aspect of the foot.


Other variants of the eosinophilic granuloma complex may be found on the same individual, e.g. ‘linear granuloma’, which is seen as a raised chord-like linear plaque, with a yellowish surface, on the caudal aspect of the thighs (Fig. 36.2). Indolent (rodent) ulcer may also be seen as an area of ulceration on the upper lip. Some individuals may also have lesions on the hard or soft palates.


image

Figure 36.2 Linear granuloma on the caudal aspect of the thigh.


Generally, affected cats do not show any signs of systemic illness, but they may have varying degrees of peripheral lymph node enlargement.


In this case the clinical examination revealed:


• Coalesced raised plaques, with erythematous, exudative, eroded surfaces (Fig. 36.3)

• Small satellite lesions of crusting on the skin surrounding the main lesion

• Moist skin surrounding the lesions, due to licking, and indicating pruritus

• Peripheral lymphadenopathy.

image

Figure 36.3 Raised plaque on the medial aspect of the thigh.




DIFFERENTIAL DIAGNOSES



• Eosinophilic granuloma complex with an underlying aetiology of:
• Adverse food reaction

• Atopic dermatitis

• Contact hypersensitivity

• Cheyletiellosis

• Pediculosis

• Demodicosis

• Dermatophytosis

• Secondary bacterial pyoderma

• Adverse drug reaction

• Viral infections (herpes virus, calicivirus, FIV, FeLV)

• Neoplasia

• Mast cell tumour

• Squamous cell carcinoma.

N.B. Flea allergy dermatitis was not included in this differential diagnosis in view of the previous thorough flea control.



CASE WORK-UP


It cannot be stressed enough that eosinophilic granuloma is not a diagnosis but a reaction pattern, and therefore the aim, particularly in cases such as this where the disease was recurrent, is to identify and correct the underlying cause. Amongst other tests, this usually involves therapeutic and diet trials to rule out the involvement of ectoparasitic and microbial diseases, and adverse food reactions. However, the clinician should be aware when undertaking such trials that despite correcting the underlying cause (e.g. avoidance of food allergens in a food allergic cat), the eosinophilic lesions may still not resolve. This is because the lesion is a source of cytokines and other factors (see ‘Aetiopathogenesis’) that not only cause tissue damage, but continue to stimulate eosinophil production in the bone marrow, recruit inflammatory cells to the damaged tissue, increase eosinophil survival time and perpetuate the lesion. Thus, it may be necessary to achieve resolution by therapeutic intervention in addition to investigation of the underlying cause. As might be expected, this complicates assessment of the response to therapeutic and diet trials. These are complex cases and it is important to warn the client at the outset of the time and commitment involved in making a definitive diagnosis.


In the first instance, the following investigations were carried out:


• An impression smear of the lesion, stained with modified Wright’s stain, revealed a mixed inflammatory cell population, mainly of eosinophils and neutrophils. Extracellular and intracellular coccoid bacteria were also present (Fig. 36.4).

• A swab sample was cultured, which revealed coagulase-negative staphylococci (speciation was not carried out on the sample).

• Blood samples for routine haematological and biochemical parameters, which were within laboratory reference ranges.

• Skin scrapes, coat brushings and fungal culture from toothbrush combing, which were all negative for ectoparasites and dermatophytes.

• Three skin samples were taken by punch biopsy for histology, one from the centre of the lesion, one from the edge of the lesions and one from the surrounding skin. (The diagnosis of eosinophilic plaque may be made on clinical appearance and cytological examination alone but histopathological examination is indicated if there is any doubt about the diagnosis and in this case ruled out a number of the other differentials.)

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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Feline eosinophilic plaque
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