LEP and obesity due to melanocortin 4 receptor deficiency: In obesity, the white adipose tissue undergoes immunological changes including macrophage infiltration resulting in a proinflammatory milieu and secretion of several cytokines and adipokines, such as tumor necrosis (TNF)-α, interleukin (IL)-17, IL-23, leptin, resistin and adiponectin, that may be important in PsA [9–11].