Onset of psoriatic arthritis in patients treated with efalizumab for moderate to severe psoriasis

Objective To investigate the nature of polyarthritis in patients with moderate to severe psoriasis undergoing treatment with efalizumab, a humanized anti‐CD11a monoclonal antibody. Methods In a multicenter study, we retrospectively analyzed patients who developed arthritis during treatment with efalizumab. The relationship between joint manifestations and psoriatic disease was addressed by using different classification criteria for psoriatic arthritis (PsA). The course of arthritis and its response to treatment were also investigated. Results Sixteen patients developed de novo inflammatory rheumatic disease, with a mean delay of 15 weeks following the start of treatment, and with exclusive asymmetric peripheral monarthritis or oligoarthritis (8 patients), inflammatory spinal disease (1 patient), or both (7 patients), associated in some cases with enthesitis and dactylitis. All patients fulfilled at least 2 different sets of classification criteria for PsA. In most of them, an improvement in skin lesions was observed at the onset of PsA, as measured using the Psoriasis Area and Severity Index (mean score 24.88 before efalizumab versus 18.78 at the time of arthritis). Efalizumab treatment was stopped in 11 patients and was followed by the elimination of rheumatologic symptoms in 1 patient, while 8 patients required treatment with nonsteroidal antiinflammatory drugs with or without methotrexate, with 2 later being switched to tumor necrosis factor α inhibitors. Reintroduction of efalizumab (2 patients) was followed by a relapse of PsA. Conclusion This study questions the role of efalizumab in the induction of PsA. It also emphasizes the discrepancy between the courses of psoriatic skin and joint manifestations under treatment. Prospective case–control studies are needed to accurately investigate the impact of efalizumab on PsA.