Systemic Vasculitis with Severe Cutaneous Manifestation as a Suspected Idiosyncratic Hypersensitivity Reaction to Fenbendazole in a Cat

A 16-month-old cat developed severe systemic vasculitis with cutaneous manifestations, suspected to be an idiosyncratic hypersensitivity reaction to fenbendazole. The cat exhibited severe anemia, thrombocytopenia, coagulopathy, and necrotic lesions, which worsened despite initial treatment, requiring surgical and further immunosuppressive therapy. Histopathology confirmed vasculitis, and the cat eventually recovered. This case was the first to document such a reaction to fenbendazole in cats and the first to use pentoxifylline for treatment, highlighting the rarity of idiopathic adverse drug reactions in cats and emphasizing cautious drug administration and monitoring.