Malassezia dermatitis in dogs and cats: Clinical features and histopathology.
Dogs and cats may develop several forms of exfoliative dermatitis as a result of their exposure to allergens. The most common causes of these types of dermatitis are mites and yeast. The m of this study was to describe the clinical features, as well as the histopathological and immunohistochemical findings in skin biopsies of the cases examined. All cases (n=8) of canine and feline exfoliative dermatitis were included in the study. A thorough clinical and histopathological examination of the skin lesions was performed. In addition, immunohistochemical analysis for CD1d, IL-13, MHC II, and FOXP3 expression was also performed. Clinical signs of the cases examined included erythematous or brown skin lesions with fine or coarse scales. Histopathological findings showed hyperkeratosis, parakeratosis, acanthosis, papillomatosis, and follicular hyperplasia, as well as hypergranulosis, eosinophils, and neutrophils. All dogs and cats with dermatitis due to yeast were diagnosed as having demodicosis, while all cases with mite dermatitis were diagnosed with demodicosis and flea dermatitis. The immunohistochemical findings revealed no differences between the groups in terms of the expression of CD1d, IL-13, MHC II, and FOXP3. However, some differences were observed in terms of the expression of these molecules between cases diagnosed as demodicosis and cases diagnosed as demodicosis and flea dermatitis. In conclusion, clinical and histopathological findings may be used to differentiate between demodicosis and mite dermatitis. This is the first study to demonstrate the usefulness of immunohistochemistry in a histopathological investigation of skin lesions.