Psoriasis is a chronic inflammatory disease of the skin with an unknown aetiology. After receiving scant consideration for quite a few years, psoriasis has now become a prominent focus for new drug development. Psoriasis is associated with multiple comorbidities including autoimmune disease, neurological disorders, cardio-metabolic diseases and inflammatory-bowel disease. This concise handbook gives an overview about psoriasis and its epidemiology. The book combines the detailed information on new psoriasis specific biomarkers identified based on the gene expression analysis. The underlying pathophysiological characteristics of each biomarker, as well as its implication in the disease mechanism are reviewed in this book.