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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 that consists of patchy, raised, red areas of skin inflammation with scaling. 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.
Who Is at Risk for Psoriatic Arthritis?
Affecting men and women equally, about 10% to 30% of people with psoriasis develop psoriatic arthritis. Psoriatic arthritis may develop at any age but usually affects people between the ages of 30 and 50. While the cause is not known, genetic factors, along with the immune system likely play a role in determining who will develop the disorder.
As many as 40% of people with psoriatic arthritis have a family history of skin or joint disease. Having a parent with psoriasis triples the chance of getting psoriasis yourself and, therefore, increases the chance of developing psoriatic arthritis.
What Causes Psoriatic Arthritis?
The cause of psoriatic arthritis is currently unknown. A combination of genetic, immune, and environmental factors is likely involved. Of patients with psoriatic arthritis who have the arthritis in the spine, a gene marker named HLA-B27 is found in about 50%. Blood testing is used 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.
Patients with psoriatic arthritis can also develop inflammation of the tendons (tendinitis); inflammation of the tendon behind the heel causes Achilles tendinitis. 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.
Are There Different Types of Psoriatic Arthritis?
There are five types of psoriatic arthritis depending on the distribution of the joints affected:
- Symmetric psoriatic arthritis
- Asymmetric psoriatic arthritis
- Distal interphalangeal predominant (DIP)
- Arthritis mutilans
It is important to know which type of psoriatic arthritis you have and to understand the characteristics so that it may be treated properly. We'll review each on the following slides.
Symmetric Psoriatic Arthritis
Symmetric psoriatic arthritis affects the same joints -- usually in multiple matching pairs -- on opposite sides of the body. Symmetric psoriatic arthritis can be disabling, causing varying degrees of progressive, destructive disease and loss of function in 50% of people with this type of arthritis. Symmetric psoriatic arthritis resembles rheumatoid arthritis.
Asymmetric Psoriatic Arthritis
Asymmetric psoriatic arthritis typically involves one to three joints in the body -- large or small -- such as the knee, hip, or one or several fingers. Asymmetric psoriatic arthritis does not affect matching pairs of joints on opposite sides of the body.
Distal Interphalangeal Predominant (DIP)
Distal interphalangeal predominant psoriatic arthritis involves primarily the small joints in the fingers and toes closest to the nail. DIP psoriatic arthritis is sometimes confused with osteoarthritis, a chronic disease that causes the deterioration of joint cartilage and bone at the joints.
Spondylitis affects the spinal column and may cause inflammation and stiffness in the neck, lower back, spinal vertebrae, or sacroiliac region (pelvic area), making motion difficult.
Arthritis mutilans is a severe, deforming, and destructive form of psoriatic arthritis that primarily affects the small joints in the fingers and toes closest to the nail. This leads to loss of function of the involved joints. Fortunately, this severe type of psoriatic arthritis is rare.
How Is Psoriatic Arthritis Diagnosed?
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. X-rays may show changes of cartilage or bone injury indicative of arthritis of the spine, sacroiliac joints, and/or joints of the hands. The blood test for the genetic marker HLA-B27, as mentioned on slide three, is sometimes performed. This marker can be found in over 50% of patients with psoriatic arthritis who have spine inflammation.
What Is the Treatment for Psoriatic Arthritis?
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 as methotrexate (Rheumatrex, Trexall), corticosteroids, and antimalarial medications (such as hydroxychloroquine [Plaquenil]) are used.
Exercise programs can be done at home or with a physical therapist and are customized according to the disease and physical capabilities of each patient. Warm-up stretching or other techniques, such as a hot shower or heat applications, are helpful to relax muscles prior to exercise. Ice application after the routine can help minimize post-exercise soreness and inflammation. In general, exercises for arthritis are performed for the purpose of strengthening and maintaining or improving joint range of motion. They should be done on a regular basis for best results.
Is There a Cure for Psoriatic Arthritis?
While there are drugs that can stop the progression of the disease, there is no cure for psoriatic arthritis. However, treatment usually resolves pain. By understanding the disorder and knowing what to expect, you can learn new ways to perform daily tasks or plan activities during the times and days you are least bothered by the effects of the disease. Once you understand and learn to predict the ways in which your body responds to psoriatic arthritis, you can use exercise and therapy to alleviate discomfort and reduce stress and fatigue.
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.