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

A 16-month-old domestic short-haired 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. Histopathology confirmed ulcerative and necrotizing dermatitis due to ischemia from thrombosis. Treatment with corticosteroids and immunosuppressive agents resolved the symptoms. This case was the first documented instance of such a reaction in a cat and highlighted the potential for fenbendazole to cause rare hypersensitivity reactions, emphasizing cautious use and monitoring. Additionally, it reported the first use of pentoxifylline in treating feline vasculitis, which was well tolerated without adverse effects.