Refractory Dermatophytosis in a Spitz Dog Successfully Managed with Posaconazole: A Case Report

Dermatophytosis is a superficial fungal skin disease of cats and dogs. The most common pathogens of small animals belong to the genera Microsporum and Trichophyton. It is an important skin disease because it is contagious and can be transmitted to people. Refractory dermatophytosis has become a disease of increasing concern in dermatological practice due to poor responses to standard antifungal therapy. The condition is characterised by chronicity, recurrence, or persistence despite adequate treatment. This report describes the clinical presentation and therapeutic management of refractory dermatophytosis in an 8-year-old intact male Spitz dog weighing 10 kg presenting with persistent alopecia, scaling, erythema, and pruritus despite multiple courses of systemic antifungal agents (itraconazole) and topical antifungal agents (2% miconazole shampoos and terbinafine-containing dusting powder). Diagnosis was confirmed by microscopic examination, culture, and punch biopsy. Due to the lack of response to standard therapy, posaconazole was initiated based on antifungal susceptibility testing (AFST). Marked clinical improvement was observed without adverse effects. This report documents a case of refractory dermatophytosis in which AFST informed the selection of posaconazole therapy. It highlights the diagnostic challenges of recurrent dermatophytosis, suggests that AFST-guided treatment strategies may help manage infections unresponsive to standard antifungal therapy, and demonstrates that posaconazole is a promising alternative antifungal agent for refractory dermatophytosis in dogs.