Asymmetric vs. Symmetric Psoriatic Arthritis

The pattern of arthritis affects diagnosis and treatment

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There are five distinct patterns of joint involvement in people with psoriatic arthritis. The two most common ones are symmetric psoriatic arthritis, in which the same joints on both sides of the body are affected, and asymmetric psoriatic arthritis, in which joints are affected with no predictable pattern. These distinctions are important in that they not only suggest the severity of the disease, but also direct diagnosis and treatment.

Psoriatic Arthritis and Inflammation

Psoriatic arthritis is an inflammatory form of arthritis integrally linked to psoriasis. In most cases, psoriasis precedes psoriatic arthritis.

Psoriasis is an autoimmune disease that targets cells in the outer layer of skin, triggering inflammation and the formation of skin plaques. Over time, the inflammation begins to "spill over" and affect other organ systems and, in the case of psoriatic arthritis, the joints.

Symptoms include joint stiffness, pain, and swelling as well as fatigue and a reduced range of motion. Joint deformity can also occur.

The extent of inflammation and, thus, the severity of one's psoriasis is what dictates whether psoriatic arthritis (if it occurs) is asymmetric or symmetric.

Up to 40% of people with psoriasis will go on to develop psoriatic arthritis, according to a 2014 review of studies in the journal Drugs. On rare occasions, psoriatic arthritis may occur on its own with no evidence of psoriasis at all.

Asymmetric

Asymmetric psoriatic arthritis appears in 35 percent of people with the condition. It is called asymmetric because the joint pain and swelling occur on one side of the body only. For example, one knee or wrist is affected, but the other knee or wrist is not.

By definition, asymmetric psoriatic arthritis is milder than its symmetric counterpart as it affects no more than five joints. The larger joints tend to be affected, though the hand and foot may also be involved. Asymmetric psoriatic arthritis will often precede symmetric psoriatic arthritis, but not always.

Psoriatic arthritis affects women and men equally, but men tend to have asymmetric disease more than women.

Symmetric

Symmetric psoriatic arthritis is characterized by the mirroring of arthritic joints on both sides of the body. It is a pattern that mimics rheumatoid arthritis and one that frequently leads to misdiagnosis. Rheumatoid arthritis differs psoriatic arthritis in that autoimmune cells directly damage joint tissues, rather than inflammation.

Symptoms range from mild to severe, but are generally more significant than asymmetric psoriatic arthritis (in part because more joints are affected). Around half of all people with symmetric psoriatic arthritis will experience some degree of disability.

Even with effective treatment, many people with asymmetric psoriatic arthritis, especially women, go on to develop symmetric psoriatic arthritis.

Diagnosis

The diagnosis is mainly based on a review of your symptoms and medical history. You have a 50/50 chance of developing psoriatic arthritis if both of your parents have it.

There are no blood tests or imaging studies that can definitively diagnose psoriatic arthritis. Imaging tests, such as X-ray and magnetic resonance imaging (MRI), can help characterize the nature and pattern of joint involvement.

If the cause remains uncertain, joint aspiration or biopsy may be used to look for proteins and amino acids (called nerve growth factor) characteristic of the disease.

As part of the diagnostic process, a rheumatologist will differentiate psoriatic arthritis from other diseases with similar symptoms. These include rheumatoid arthritis (which can be differentiated with a rheumatoid factor blood test) and gout (which can be differentiated by the presence of uric acid crystals in joint fluid). Reactive arthritis, septic arthritis, and osteoarthritis may also be included in the differential diagnoses.

Treatment

The treatment of asymmetric or symmetric psoriatic arthritis is essentially the same. There is no cure for the disease, so the treatment will be focused on the alleviation of inflammation to reduce pain, maintain range of motion, and slow the progression of the disease.

Though symmetrical psoriatic arthritis tends to be more severe, the course of treatment will ultimately be based on your level of pain, mobility, disability as well as your age, health, and quality of life.

Treatment options include:

Severe cases may require surgery to improve joint function and reduce pain. Options include arthroscopic debridement, synovectomy, arthrodesis (joint fusion), and joint replacement.

An effort should also be made to identify your disease triggers. One such example is stress. By better managing your stress levels with mind-body therapies like guided imagery or progressive muscle relaxation (PMR), you may be able to reduce the frequency or duration of acute flares.

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Article Sources

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  5. Raychaudhuri SP, Raychaudhuri SK, KA Atkuri, et al. Nerve growth factor: A key local regulator in the pathogenesis of inflammatory arthritis. Arthritis & Rheumatism. 2011 Jul;63(11):3243-52. doi:10.1002/art.30564

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  7. Arthritis Foundation. Managing Psoriatic Arthritis Flares.

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