Psoriasis is a hereditary disorder of the skin affecting up to 2% of the population. It can take many forms, but presents with thick, scaly red plaques on the elbows, knees, scalp and trunk. Other forms affect only the nails, hands or feet. Irregularities in immune function in the skin are likely responsible for psoriasis. Psoriasis can also affect joints, causing arthritis that can be quite debilitating. Men and women are affected evenly, though the disorder is more prevalent in Caucasians. There is no cure for psoriasis, but it can be controlled through many new and some older medications and interventions.