Book excerpt: Some people with psoriasis can also develop psoriatic arthritis, when the immune system attacks the joints as well, causing inflammation. Like psoriasis, psoriatic arthritis symptoms flare and subside, vary from person to person, and even change locations in the same person over time. Psoriatic arthritis can affect any joint in the body, and it may affect just one joint, several joints or multiple joints. For example, it may affect one or both knees. This issue will include articles on Genetic and Epigenetic aspects of psoriatic arthritis, Clinical features and diagnostic considerations in psoriatic arthritis, Natural history, prognosis and socioeconomic aspects of psoriatic arthritis, Etiology and pathogenesis of psoriasis and many more!