New-onset, debilitating arthritis in psoriasis patients receiving efalizumab

Efalizumab is a humanized anti-CD11a monoclonal IgG(1) antibody approved for the treatment of moderate-to-severe plaque psoriasis. This case report describes two cases of new-onset debilitating psoriatic arthritis in patients with plaque psoriasis on long-standing efalizumab therapy, despite the fact that their skin disease was in remission. Although during the clinical trials, involving over 2,700 study subjects, arthralgia was seen only at a rate of 1-2% higher than in those subjects receiving placebo, the cases presented here are interesting in that it appears that efalizumab treatment 'uncoupled' the psoriatic arthritic component from the cutaneous disease. It can be speculated that a possible mechanism for efalizumab-induced psoriatic arthritis is related to the blockade of regulatory T cells from joint tissue.