Adult onset Still’s disease (AOSD) is a seronegative polyarthritis associated with rash and fever. 1 The innate immune system has been implicated in its pathogenesis and hypersecretion of interleukin 1 (IL-1) has been associated with increased disease activity. 2 We report the first successful use of rilonacept, a long-acting IL-1 Trap, in the management of three patients with refractory AOSD. Rilonacept is a soluble dimeric fusion protein (IL-1 receptor extracellular domain+ hIgG1-Fc) administered as a weekly subcutaneous injection (220 mg loading dose and 160 mg maintenance dose). 3 Patient 1 was a 41 year-old woman who presented with spiking fevers, sore throat, urticaria, arthritis and splenomegaly accompanied by leucocytosis, elevated erythrocyte sedimentation rate (> 100 mm/h), increased lung function tests and hyperferritinaemia (8442 ng/ml). She was diagnosed with AOSD and partially responded to methotrexate (MTX), high-dose prednisone (80 mg/day), azathioprine (100 mg/day), leflunomide (20 mg/day) and anakinra (100 mg twice daily). A switch from anakinra to rilonacept for 18 months led to complete remission (with partial improvement seen after 1 month) and discontinuation of MTX, prednisone and, for the last 6 months, rilonacept. Patient 2 was a 36 year-old woman with daily spiking fevers, polyarthritis affecting the ankles, knees, wrists, elbows and shoulders, and a recurrent maculopapular rash on the upper back and shoulders, elevated ferritin (4253 ng/ml) and multiple treatment failures with prednisone and MTX (20 mg/week). A year later she responded only partially to anakinra (200 mg/day). The switch to rilonacept resulted in rapid (1 month) amelioration of the rash, arthritis and hyperferritinaemia (67.3 ng/ml), with long remission (26 months) interrupted by two flares of lesser severity.

Patient 3 was a 44 year-old woman with quotidian fever, arthritis of the knees, wrists and hands and erythema of the upper chest and lower extremities who was normoferritinaemic (71.7 ng/ml). Combination treatment with prednisone (1 mg/kg for 4 years), MTX (20 mg/week for 4 months) and either anakinra (100 mg/daily for 6 weeks) or intravenous abatacept (750 mg/month for 3 months) failed to control the symptoms. The switch to rilonacept led to a significant improvement in the rash and arthritis, allowed for prednisone dose tapering (20 mg/day) and weight loss (22 kg) and prolonged remission that lasted 16 months.