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Both gene and protein expression of IL-1 are highly upregulated in skin and synovium of patients with psoriatic arthritis (PsA) and psoriasis. IL-1 is known to play a key role in keratinocyte activation, matrix metalloproteinase upregulation, differentiation of osteoblast precursors into mature osteoblasts, angiogenesis and the development of erosive disease. Thus, the purpose of the study is to assess the effects of IL-1 inhibition on the clinical features of psoriasis and PsA disease activity, on synovial and cutaneous immunohistology and on magnetic resonance imaging (MRI) features of an affected knee joint.