A Life-Threatening Abscess in a Patient Treated with a Tumour Necrosis Factor-Alpha Antagonist: A Case Report

A 25-year-old man with a 3-year history of ankylosing spondylitis presented with a sudden onset of pain in his left thigh. His ankylosing spondylitis had been treated for 2 years with the tumour necrosis factor-alpha (TNF-alpha) antagonist infliximab. The initial diagnosis was a muscular tear, and non-steroidal anti-inflammatory drugs were prescribed. 40 days later, the patient had tender swelling with warmth and light redness on his left thigh. His knee function had decreased markedly. His C-reactive protein level was 320 mg/l and white cell count was 30.4 x10(9)/l, indicating severe infection. Magnetic resonance imaging revealed a loculated fluid collection in the quadriceps musculature measuring 30 cm. Hyperintensity seen on T1-weighted images was suggestive of infection. The infliximab therapy was stopped and repeated debridement and drainage performed, with about 2.5 litres of pus evacuated. Flucloxacillin was administered for 2 weeks. The wound was closed 9 days later. The patient was discharged 20 days after surgery. An alternative immunosuppressive therapy--abatacept--was introduced. At the 18-month follow-up, the patient reported only light discomfort in the thigh during exercise, with a mildly impaired range of knee movement. No infectious complications recurred.