Morphea-Like Lesion Following Topical Endectocide Application in a Cat

A 3-year-old male Persian cat developed a localized morphea-like scleroderma lesion after the topical application of a solution containing praziquantel and emodepside. The lesion, characterized by a nonpruritic, well-demarcated alopecic plaque at the application site, showed histological signs of fibrosing dermatitis. Systemic treatment with pentoxifylline was ineffective, but topical minoxidil 5% led to complete hair regrowth and lesion resolution within 60 days. Although the relationship between the lesion and the topical solution could not be definitively proven, it was classified as a 'possible' adverse drug reaction according to the Naranjo scale. This case may represent the first documented sclerodermoid reaction to these substances in veterinary medicine and is the second report of a morphea-like lesion in a cat.