Psoriasis is a common skin condition with some systemic involvement resulting from a malfunction of the immune system. Psoriasis is most commonly seen on the elbows, knees, scalp and trunk but it can develop anywhere. It is characterized as an increase in skin production resulting in plaques developing on the skin. Treatment for psoriasis may vary depending on the severity of the disease. Treatments include topical steroid and vitamin D creams, systemic therapies such as methotrexate, and also biologic medications such as Enbrel or Humira. Phototherapy is also a treatment for psoriasis which involves ultraviolet light exposure in a controlled setting. Psoriasis may potentially also result in psoriatic arthritis or joint pain.