Background - Dermoscopy is a noninvasive technique allowing rapid magnified in vivo observation of the skin and structures that lie beneath the skin surface. Various congenital and acquired hair shaft abnormalities may also be evaluated by dermoscopy. Additionally, characteristic features of Microsporum canis-induced tinea capitis and trichotillomania in humans have been reported. Objectives - To describe the dermoscopic findings observed in cats with patchy alopecia due to M. canis infection and in cats with self-inflicted hair loss. Animals - Twenty-four client-owned cats presented at a veterinary referral practice. Methods - Dermoscopy was performed with a hand-held nonpolarized light dermoscope at 10-fold magnification. The glass plate of the dermoscope was applied gently to the lesions and no sedation was required. Results - Twelve cats were diagnosed with dermatophytosis and 12 with self-induced alopecia due to other causes. At 10-fold magnification, the most characteristic findings observed in circumscribed lesions of cats with dermatophytosis were opaque, slightly curved, broken hairs of a homogeneous thickness (comma-like structures) and a variable amount of brown-to-yellow greasy scales. In cats with self-induced alopecia, multiple hairs with a normal shaft cleanly broken at different lengths, short tufts of hairs broken at an equal level and hook-like and coiled hairs were observed. Conclusions and clinical importance - This observational descriptive study suggests that dermoscopy may represent a helpful noninvasive in vivo technique in the differential diagnosis of patchy alopecia in cats.
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