Carbimazole-associated hypersensitivity vasculitis in a cat

Feline hyperthyroidism can be treated medically, surgically or with radioactive iodine. Carbimazole inhibits both triiodothyronine and thyroxine synthesis in the thyroid gland and reported side effects include mild eosinophilia, leucopenia and lymphocytosis, thrombocytopenia, elevated liver enzyme activities, gastrointestinal signs and skin abnormalities. This case report describes a cat with carbimazole-associated apparent hypersensitivity vasculitis causing digital and tail necrosis, with multiple renal infarcts. Withdrawal of carbimazole resulted in stable disease.