Clinical case challenge
A 5-year-old sprayed female domestic short haired cat is brought to her veterinarian for evaluation of raised pink lesions on the medial thighs of 2 weeks duration. The owners report that she is a healthy cat that lives indoors but occasionally has access to a screened porch. There are no other cats in the household. She is up-to-date on her vaccines and is fed a high quality, nutritionally balanced, commercial diet.
The owners note that they see her grooming her ventral abdomen, inguinal region and medial thighs fastidiously on a regular basis, and she has done so since she was two years of age.
Multifocal 0.5 to 1cm circular to ovoid raised, coalescing, alopecic plaques are noted on both medial thighs. A mild exudate is noted on their surface. The surrounding hairs on her medial thighs are markedly barbered. All other parameters are within normal limits and the patient appears to be otherwise healthy.
Fig 1: Raised, coalescing plaques on the left medial thigh
What diagnostic tests would you elect to perform?
Impression smears are taken of the lesions. Cytology reveals the presence of degenerate neutrophils, scant intracellular cocci, and a moderate number of eosinophils.
Punch biopsies of the lesions are also performed. Dermatohistopathology shows numerous epidermal vacuoles filled with eosinophils as well as a large number of eosinophils scattered throughout the superficial dermis. The findings are classic for eosinophilic plaques.
Fig 2: Eosinophil-filled epidermal vacuoles typical of eosinophilic plaques
Eosinophilic plaques are a reaction pattern seen as part of the feline eosinophilic dermatoses complex. These lesions represent a manifestation of allergic skin disease unique to cats. When eosinophilic plaques, eosinophilic granulomas, and/or indolent ulcers are noted, a full work-up for allergic dermatitis is warranted, starting with the implementation of regular monthly oral or topical flea preventatives. In this case, even though the patient lives primarily indoors, she continues to have potential contact with fleas through the screened porch. If lesions persist despite adequate ectoparasite control, a dietary elimination trial lasting eight weeks should be started. Prescription novel protein diets and hydrolyzed diets are superior to over-the-counter limited ingredient diets for trial process. Finally, if no resolution is noted despite management of ectoparasites and the completion of a strict elimination diet trial, a diagnosis of atopic dermatitis is made.
This patient was treated with cefpodoxime and a tapering course of methylprednisolone for the secondary bacterial overgrowth, inflammation and pruritus. Monthly topical treatment using selamectin was implemented at the same time as an eight week elimination diet trial using a rabbit-based diet. Lack of response prompted the initiation of oral cyclosporine, which led to a resolution of clinical signs.