Psoriasis

What is psoriatic arthritis?

Psoriatic arthritis is a chronic disease characterized by inflammation of the skin (psoriasis) and joints (arthritis). Psoriasis is a common skin condition affecting 2% of the Caucasian population in the United States. It features patchy, raised, red areas of skin inflammation with scaling. Psoriasis often affects the tips of the elbows and knees, the scalp, the navel, and around the genital areas or anus. Approximately 10% of patients who have psoriasis also develop an associated inflammation of their joints. Patients who have inflammatory arthritis and psoriasis are diagnosed as having psoriatic arthritis.

The onset of psoriatic arthritis generally occurs in the fourth and fifth decades of life. Males and females are affected equally. The skin disease (psoriasis) and the joint disease (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. In some patients, the diagnosis of psoriatic arthritis can be difficult if the arthritis precedes psoriasis by many years. In fact, some patients have had arthritis for over 20 years before psoriasis eventually appears! Conversely, patients can have psoriasis for over 20 years prior to the development of arthritis, leading to the ultimate diagnosis of psoriatic arthritis.

Psoriatic arthritis is a systemic rheumatic disease that also can cause inflammation in body tissues away from the joints other than the skin, such as in the eyes, heart, lungs, and kidneys. Psoriatic arthritis shares many features with several other arthritic conditions, such as ankylosing spondylitis, reactive arthritis (formerly known as Reiter's syndrome), and arthritis associated with Crohn's disease andulcerative colitis. All of these conditions can cause inflammation in the spine and other joints, and the eyes, skin, mouth, and various organs. In view of their similarities and tendency to cause inflammation of the spine, these conditions are collectively referred to as "spondyloarthropathies."

What causes psoriatic arthritis?

The cause of psoriatic arthritis is currently unknown. A combination of genetic, immune, and environmental factors are likely involved. In patients with psoriatic arthritis who have arthritis of the spine, a gene marker named HLA-B27 is found in about 50% of cases. Blood testing is now available to test for the HLA-B27 gene. Several other genes have also been found to be more common in patients with psoriatic arthritis. Certain changes in the immune system may also be important in the development of psoriatic arthritis. For example, the decline 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 in these patients. The importance of infectious agents and other environmental factors in the cause of psoriatic arthritis is being investigated by researchers.

What are psoriatic arthritis symptoms and signs?

In most patients, the psoriasis precedes the arthritis by months to years. The arthritis frequently involves the knees, ankles, and joints in the feet. Usually, only a few joints are inflamed at a time. The inflamed joints become painful, swollen, hot, and red. Sometimes, joint inflammation in the fingers or toes can cause swelling of the entire digit, giving them the appearance of a "sausage." Joint stiffness is common and is typically worse early in the morning. Less commonly, psoriatic arthritis may involve many joints of the body in a symmetrical fashion, mimicking the pattern seen in rheumatoid arthritis. Psoriatic arthritis can also cause inflammation of the spine (spondylitis) and the sacrum, causing pain and stiffness in the low back, buttocks, neck, and upper back. In rare instances, psoriatic arthritis involves the small joints at the ends of the fingers. A very destructive form of arthritis called "mutilans" can cause rapid damage to the joints. Fortunately, this form of arthritis is rare in patients with psoriatic arthritis.

Patients with psoriatic arthritis can also develop inflammation of the tendons (tendinitis) and around cartilage. Inflammation of the tendon behind the heel causes Achilles tendinitis, leading to pain with walking and climbing stairs. Inflammation of the chest wall and of the cartilage that links the ribs to the breastbone (sternum) can cause chest pain, as seen in costochondritis.

Aside from arthritis and spondylitis, psoriatic arthritis can cause inflammation in other organs, such as the eyes, lungs, and aorta. Inflammation in the colored portion of the eye (iris) causes iritis, a painful condition that can be aggravated by bright light as the iris opens and closes the opening of the pupil. Corticosteroids injected directly into the eyes are sometimes necessary to decrease inflammation and prevent blindness. Inflammation in and around the lungs (pleuritis) causes chest pain, especially with deep breathing, as well as shortness of breath. Inflammation of the aorta (aortitis) can cause leakage of the aortic valve valves, leading to heart failure and shortness of breath.

Acne and nail changes are commonly seen in psoriatic arthritis. Pitting and ridges are seen in fingernails and toenails of 80% of patients with psoriatic arthritis. Interestingly, these characteristic nail changes are observed in only a minority of psoriasis patients who do not have arthritis. Acne has been noted to occur in higher frequency in patients with psoriatic arthritis. In fact, a new syndrome has been described, characterized by inflammation of the joint lining (synovitis), acne and pustules on the feet or palms, thickened and inflamed bone (hyperostosis), and bone inflammation (osteitis). This syndrome is therefore given the eponym SAPHO syndrome.

What is the treatment for psoriatic arthritis?

The treatment of the arthritis aspects of psoriatic arthritis is discussed below. The treatment of psoriasis and the other involved organs is beyond the scope of this article.

Generally, the treatment of arthritis in psoriatic arthritis involves a combination of anti-inflammatory medications (NSAIDs) and exercise. If progressive inflammation and joint destruction occur despite NSAIDs treatment, more potent medications such asmethotrexate (Rheumatrex, Trexall), corticosteroids, and antimalarial medications (such as hydroxychloroquine, or Plaquenil) are employed.

Antimalarial medication such as hydroxychloroquine (Plaquenil) is also used for persistent psoriatic arthritis. Its potential side effects include injury to the retina of the eye. Regular ophthalmologist examinations are suggested while using this medication.

Injectable gold (Solganal) and oral gold auranofin (Ridaura) have potential side effects including bone-marrow suppression which can lead to anemia and low white blood counts and adverse effects on the kidney, causing loss of protein or blood in the urine. Gold injections have lost favor as a form of treatment since methotrexate has become popular.

Sulfasalazine (Azulfidine) is an oral sulfa-related medicine that has also been helpful in some patients with persistent psoriatic arthritis. Traditionally, Azulfidine has been an important agent in the treatment of ulcerative and Crohn's colitis. It should be taken with food, as it too can cause gastrointestinal upset.

Research has demonstrated effective treatment of both psoriasis and psoriatic arthritis with leflunomide (Arava), a medication that is also used for the treatment of rheumatoid arthritis.

Medications that block the chemical known as tumor necrosis factor (TNF) are another treatment option for severe cases. The TNF-blockers etanercept (Enbrel), infliximab(Remicade), and adalimumab (Humira) can be very effective for severe psoriatic arthritis and they can significantly improve or eradicate both the psoriasis and the arthritis as well as stop progressive joint damage.

Corticosteroids are potent anti-inflammatory agents. Corticosteroids can be given by mouth (such as prednisone) or injected (cortisone) directly into the joints to reduce inflammation. They can have side effects, especially with long-term use. These include thinning of the skin, easy bruising, infections, diabetes, osteoporosis and, rarely, bone death (necrosis) of the hips and knees.

While the relationship between the skin disease and joint disease is not clear, there are reports of improvement of the arthritis simultaneously with clearing of the psoriasis. Patients with psoriasis can benefit by direct sunlight exposure and are often treated with direct ultraviolet light therapy.

Finally, patients who have severe destruction of the joints may be candidates for orthopedic surgical repair. Total hip joint replacement and total knee joint replacement surgery are now commonplace in hospitals.

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.

Psoriatic Arthritis At A Glance

• • 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/)