15% to 20% of the people suffering from psoriasis also develop symptoms of arthritis and this together is known as psoriatic arthritis. This develops in the people within the age group of 30 to 50 years. Arthritis develops after some years of psoriasis.

Pain in the joints all throughout the body, swelling in the joints followed by severe pain and stiffness of the body are some of the primary symptoms of psoriatic arthritis. Arthritis mutilans is the most severe and least form of arthritis which disables the joints and destroys small bones of the body especially of fingers resulting in permanent deformity and disability. Inflammation of the skin is the primary sign seen in person affected with psoriatic arthritis. Elbows, feet, knee and ankles are some of the commonly affected area by psoriatic arthritis.

Psoriatic joints can also affect tendons and ligaments of the body. Joints in the back are also affected by it. It is difficult to diagnose psoriatic arthritis in the early stage and one common symptom that is found in people suffering from it is development of pits on the nails of the fingers or of the toes. Psoriasis is considered as autoimmune disease developed as a result of reaction of body immune system.