Overview of Psoriatic Arthritis
Psoriatic arthritis (PsA) is a disease in which the immune system attacks normal cells in the body, causing damage and inflammationan autoimmune disorder. PsA results in pain, stiffness, and swelling in the joints, and scaly, itchy patches on the skin. Psoriatic arthritis is related to the chronic skin disorder psoriasis.
Joint pain caused by psoriatic arthritis often affects the wrists, knees, ankles, fingers, and toes. Scaly patches of skin commonly develop on the elbows, knees, and scalp. PsA is a chronic (long-lasting) disorder that is often characterized by flares (worsening of symptoms) and remissions (improvement in symptoms). In approximately 80 percent of cases, psoriatic arthritis also involves the fingernails and toenails (e.g., loosening of the nails, development of ridges and pits).
Types of Psoriatic Arthritis
There are 3 major types of psoriatic arthritis:
- Asymmetric inflammatory arthritis (resembles reactive arthritis and affects 1 or more joints causing inflammation and calcification in the affected joints)
- Symmetric arthritis (resembles rheumatoid arthritis and affects multiple joints on both sides of the body)
- Psoriatic spondylitis (similar to ankylosing spondylitis in which the spine and/or large joints such as the hip or shoulder are affected)
Asymmetric inflammatory arthritis usually affects the fingers and toes and often results in a "sausage-like" appearance (called dactylitis). In most cases of this type, fewer than 5 joints are affected.
Symmetric arthritis, which is relatively common, usually affects the hands, wrists, feet, and ankles. Although this type is similar to rheumatoid arthritis, it is usually less severe.
Psoriatic spondylitis, which is more common in men, affects the spine and the sacroiliac joints (i.e., the joints between the base of the spine and the pelvis) and results in back pain and difficulty walking.
Incidence and Prevalence of Psoriatic Arthritis
Psoriatic arthritis is the second most common inflammatory joint disease. According to the National Institutes of Health (NIH), approximately 1 million people in the United States have the psoriatic arthritis, and according to the National Psoriasis Foundation, this number reflects 1030 percent of patients who have psoriasis.
Psoriatic arthritis affects men and women equally and usually develops between the ages of 20 and 50. The disorder can occur at any age. In the United States, PsA is more prevalent in Caucasians than in other races.
Psoriatic arthritis accounts for approximately 1020 percent of arthritis cases in children. Juvenile psoriatic arthritis occurs most often in girls about 10 years of age.