We report a case of vasculitis after Prosorba treatment in a patient with rheumatoid arthritis. The patient is a 66-year-old white male with long standing rheumatoid arthritis and hepatitis B. He was treated with the standard regimen for Prosorba treatment. He improved and met criteria for an American College of Rheumatology (ACR) 20% response. While on therapy he developed a nonhealing ulcer. Approximately 2 weeks after treatment was completed, he developed palpable purpura and mononeuritis multiplex. Deep dermal biopsy confirmed the presence of both small and medium vessel vasculitis. Nerve conductions studies were consistent with neuropathic conduction delays. He was treated with 1mg/kg/day of oral prednisone.Prosorba has been reported to cause leukocytoclastic vasculitis during treatment, but has not been noted to involve medium sized vessels. This patient’s history and presentation are most consistent with rheumatoid arthritis associated vasculitis, though the Prosorba treatment cannot be ruled out as a cause or a contributing factor. Importantly, although Prosorba treated his synovitis, it did not prevent concomitant vasculitis.