Psoriasis is a chronic, immune-mediated, inflammatory relapsing systemic skin disorder that predominantly involves the skin, nails, and joints with intermittent remissions. The disease is resulting from a polygenic predisposition, combined with environmental triggering factors. The worldwide prevalence of psoriasis is estimated to be approximately 2-3% . Prevalence varies according to race, geographic location and environmental factors . About two-thirds of affected individuals suffer from mild psoriasis, whereas about one- third have a more severe involvement.