During the past two decades, IL-6 has been reported to be associated with the pathogenesis of psoriasis.133,148 But only till recently, the expression of the IL-6 gene has been regarded as a marker for the pathological state of psoriasis and psoriatic arthritis.149 In psoriasis, the source of IL-6 includes almost all stromal cells, including keratinocytes, fibroblasts, endothelial cells, and immune cells such as dendritic cells, macrophages, and Th17 cells.150,151 IL-6 acts through interacting with IL-6R. Here, IL6 is linked to psoriatic arthritis.