What is psoriatic arthritis?
Psoriatic arthritis is a chronic disease characterised by inflammation of the skin (psoriasis) and joints (arthritis). Psoriasis is a common skin condition affecting approximately 2% of the population, this skin condition is characterised by patchy, raised, red areas of skin inflammation with scaling. Psoriasis can affect any part of the body, but most often affects the tips of the elbows and knees, the scalp, the navel, and around the legs, hands and nails. Apprimately 5 – 7% of psoriasis patients also develop an associated inflammation of their joints, a condition we know as psoriatic arthritis. Patients who have inflammatory arthritis and psoriasis together, are diagnosed as having psoriatic arthritis.
The onset of psoriatic arthritis most often occurs when a person is in their fourties of fifties, and males and females can both be equally affected. Both the psoriasis and the arthritis often appear separately. In fact, the skin disease precedes the arthritis in nearly 80% of patients. However, the arthritis may precede the psoriasis in up to 15% of patients. It can be cery difficult to diagnose psoriatic arthritis, because both arthritis and psoriasis may occur in a patient but may manifest many years apart.
Psoriatic arthritis is a particuclar form of arthritis sometimes associated with other auto-immune diseases, such as ankylosing spondylitis, reactive arthritis (Reiter’s syndrome), and arthritis associated with inflammatory bowel disease (IBD) such as Crohn’s disease and ulcerative colitis. All of these auto-immune conditions can cause inflammation in the spine and other joints, and the eyes, skin, mouth, and various organs.
What causes psoriatic arthritis?
The interesting point with auto-immune conditions is that there are “no known causes” as far as conventional medicine is concerned, and the cause of psoriatic arthritis is currently unknown. A combination of genetic, immune, and environmental factors are likely involved. There is a gene involved, and the HLA-B27 gene is found in over half of those who have arthritis of the spine, and recently a blood-test has become available to quickly test for this marker. With ankylosing spodylitis, HLA-B17 is also apparent.
Some experts believe that there are infectious agents responsible for auto-immune conditions such as psoriatic arthritis, because certain changes in the immune system may be important in the development of psoriatic arthritis. For example, a reduction in the number of immune cells called helper T cells in people with AIDS may play a role in the development and progression of psoriasis and psoriatic arthritis in these patients.
How does the doctor diagnose psoriatic arthritis?
Psoriatic arthritis is a diagnosis made mainly on clinical grounds, based on a finding of psoriasis and the typical inflammatory arthritis of the spine and/or other joints. There is no laboratory test to diagnose psoriatic arthritis. Blood tests such as sedimentation rate may be elevated and merely reflect presence of inflammation in the joints and other organs of the body. Other blood tests such as rheumatoid factor are obtained to exclude rheumatoid arthritis. When one or two large joints (such a knees) are inflamed, arthrocentesis can be performed. Arthrocentesis is an office procedure whereby a sterile needle is used to withdraw (aspirate) fluid from the inflamed joints. The fluid is then analyzed for infection, gout crystals, and other inflammatory conditions. X-rays may show changes of cartilage or bone injury indicative of arthritis of the spine, sacroiliac joints, and/or joints of the hands. Typical X-ray findings include bony erosions resulting from arthritis. The blood test for the genetic marker HLA-B27, mentioned above, is often performed. This marker can be found in over 50% of patients with psoriatic arthritis who have spine inflammation.
What does the future hold for patients with psoriatic arthritis?
The future treatment of psoriatic arthritis will evolve as more effective and safe medicines are developed. Recently, it has been shown that vitamin D might actually improve the arthritis of psoriatic arthritis. Other areas of research involve treatment with medications that can alter the immune system of patients with psoriatic arthritis. As the immune system changes and genetics are better defined in this illness, the efficacy of these medical treatments will improve.
- About one in 10 people with psoriasis also develop inflammation of joints (psoriatic arthritis).
- The first appearance of the skin disease (psoriasis) can be separated from the onset of joint disease (arthritis) by years.
- Psoriatic arthritis belongs to a group of arthritis conditions that cause inflammation of the spine (spondyloarthropathies).
- Patients with psoriatic arthritis can develop inflammation of tendons, cartilage, eyes, lung lining, and, rarely, the aorta.
- The arthritis of psoriatic arthritis is treated independently of the psoriasis, with exercise, ice applications, medications, and surgery.
For more information about psoriatic arthritis, please visit the following sites:
National Psoriasis Foundation/USA (http://www.psoriasis.org/)
- Koopman, William, et al., eds. Clinical Primer of Rheumatology. Philadelphia: Lippincott Williams & Wilkins, 2003.
- Ruddy, Shaun, et al., eds. Kelley’s Textbook of Rheumatology, 6th ed. Philadelphia: Saunders, 2001.
Last Editorial Review: 12/03/2011