A difficult to diagnose arthritis unless the skin rash – psoriasis – is already present. Psoriatic arthritis is an inflammatory arthritis associated with pain, swelling, and morning stiffness that presents as arthritis in a single joint, arthritis in the low back/sacroiliac joints, as a rheumatoid pattern of arthritis frequently associated with nail pitting. Psoriatic arthritis is classified as a “seronegative” arthritis in that serum (blood) testing for rheumatoid arthritis and connective tissue diseases is negative. In some cases, the arthritis appears before the psoriasis does. Recently several breakthroughs has identified psoriasis and psoriatic arthritis as an immunologically controlled disease which is why treatment with drugs such as sulfasalazine, methotrexate, Humira, Enbrel, Otezla, Stelara, and Cosentyx have been advanced to treat not only extensive skin disease but also the arthritis associated with Psoriasis.