Abstract
Psoriatic arthritis (PsA) is a chronic inflammatory disease characterized by skin and joint involvement. The disease may present with various joint pattern involvement, which sometimes may lead to joint destruction and deformity. Early diagnosis and treatment with disease-modifying anti-rheumatic drugs may prevent joint deformity. Recently there are many new treatment options including biologic drugs. Ustekinumab, an interleukin 12/23 inhibitor, has proven efficacy in the treatment of psoriatic arthritis. Like other biologic drugs (anti-TNF-α), there are contradictory data about the safety of ustekinumab and possible relationship with cancer development. Herein we report the development of chronic lymphocytic leukemia in a patient with PsA treated with ustekinumab.