Psoriatic arthritis is classified as one of the spondyloarthropathies (a group of conditions linked to spine arthritis). It is important to be accurately diagnosed with psoriatic arthritis so that treatment options can be considered early in the course of the disease. There are 10 things you should know about psoriatic arthritis.
1 - Psoriatic arthritis is a type of arthritis associated with the skin disease psoriasis.
Psoriatic arthritis is a chronic type of arthritis. In some patients, symptoms associated with psoriatic arthritis are mild. In those patients with mild disease, the symptoms can come and go. For other patients with psoriatic arthritis, the course of the disease is more persistent.
2 - Psoriatic arthritis can affect any joint in the body.
Typically, psoriatic arthritis affects large joints of the lower extremities, distal joints of the fingers and toes, as well as the back and sacroiliac joints. There are 5 clinical patterns of psoriatic arthritis which are not mutually exclusive and may evolve from one to another:
- asymmetrical monoarticular and oligoarticular arthritis
- symmetrical polyarticular arthritis
- distal interphalangeal joint involvement
- arthritis mutilans
- axial or spondylitis type
Each type is explained in Psoriatic Arthritis - Fast Facts.
3 - About 40 percent of psoriatic arthritis patients have a family history of psoriasis or arthritis.
The cause of psoriatic arthritis is still unknown. Patients with a family history of psoriasis or arthritis support the theory that genetic factors may be related to the cause. Environmental triggers may also play a role. For example, psoriasis can be triggered by strep throat in some cases.
4 - About 15 percent of people with psoriasis eventually develop psoriatic arthritis.
The symptoms of psoriasis and chronic joint inflammation often develop separately for psoriatic arthritis patients. In 85 percent of psoriatic arthritis patients, symptoms of psoriasis develop before arthritis symptoms. Arthritis develops before psoriasis in up to 15 percent of psoriatic arthritis patients. Psoriasis and arthritis can develop years apart.
5 - Psoriatic arthritis may be misdiagnosed as gout or rheumatoid arthritis.
Gout and rheumatoid arthritis share some of the signs and symptoms associated with psoriatic arthritis. Tests must be performed to rule out the other conditions. Painful, swollen joints are common to all three of the conditions mentioned. Skin and nail changes consistent with psoriasis help to pin down the diagnosis. Skin biopsies are also sometimes obtained to help diagnose psoriatic arthritis.
6 - Psoriatic arthritis, unlike rheumatoid arthritis, may only need to be treated when symptoms arise.
When symptoms subside and psoriatic arthritis is less active, it may be possible to stop treatment for some patients until symptoms re-appear. NSAIDs (nonsteroidal anti-inflammatory drugs) are typically the first line of treatment for psoriatic arthritis. DMARDs (disease-modifying anti-rheumatic drugs) may be added to the treatment course. Biologic drugs are also among the treatment options.
7 - There are factors which are predictive of a worse prognosis for psoriatic patients.
The prognosis for psoriatic arthritis patients is worse if they have:
- extensive skin involvement
- strong family history of psoriasis
- female gender
- disease onset at younger than 20 years of age
- expression of genes HLA-B27, HLA-DR3, HLA-DR4
- polyarticular (i.e., arthritis affecting several joints) or erosive arthritis (i.e., joint damage from inflammation)
8 - About 2 percent of the Caucasian population in North America has psoriasis. Of those people, 5 to 7 percent have inflammatory arthritis in some form.
According to the Arthritis Foundation, 95 percent of people with psoriatic arthritis have swelling in joints outside of the spine and more than 80 percent have nail lesions. Psoriatic arthritis usually develops between 30 to 50 years of age. Men and women seem to have equal risk for developing psoriatic arthritis.
9 - There is a 50-fold increased risk of developing psoriatic arthritis in first-degree relatives of patients who have the disease.
Researchers have also determined that in identical twins, there is 70 percent concordance (i.e., the degree of similarity in a pair of twins with regard to the presence or absence of a particular disease) for psoriasis. Interestingly, there is a two-fold increased risk of transmitting psoriatic arthritis by an affected father compared to an affected mother.
10 - No laboratory tests or specific X-ray results offer definitive diagnostic criteria for psoriatic arthritis.
Laboratory tests for nonspecific inflammation (i.e., sedrate and CRP) may be elevated when psoriatic arthritis is active. Typically, the psoriatic arthritis patient is negative for rheumatoid factor. If rheumatoid factor is positive, it may be a case of psoriasis combined with rheumatoid arthritis, rather than a case of psoriatic arthritis.
Psoriatic Arthritis. Patient Education - American College of Rheumatology. May 2004.
Psoriatic Arthritis. Don Martin, M.D., Johns Hopkins Arthritis Center. July 3, 2007.