Asymmetric vs. Symmetric Psoriatic Arthritis

How 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 are symmetric psoriatic arthritis, in which the same joints on both sides of the body are affected, and asymmetric psoriatic arthritis, in which a few joints are affected sporadically. These distinctions are important in that they not only suggest the severity of the disease but also help direct the diagnosis and treatment.

Distal interphalangeal predominant, spondylitis, and arthritis mutilans are the three less common—albeit potentially more serious—forms of psoriatic arthritis.

What Is Psoriatic Arthritis?

Psoriatic arthritis is an inflammatory form of arthritis integrally linked to psoriasis. Psoriasis is an autoimmune disease in which the immune system targets cells in the outer layer of skin, triggering inflammation and the formation of skin plaques. Over time, the inflammation will begin to affect other organ systems. Psoriatic arthritis is the result when the joints are affected.

Up to 40 percent of people with psoriasis will go on to develop psoriatic arthritis, says a 2014 review of studies in the journal Drugs

Of these, the vast majority will have some degree of skin involvement. On rare occasion, psoriatic arthritis may be the first and only symptom with no evidence of psoriasis at all.

The location and severity of psoriatic arthritis can vary from person to person. Common symptoms include joint stiffness, pain, and swelling as well as fatigue and a reduced range of motion. Certain types of psoriatic arthritis may cause swollen, sausage-like finger (dactylitis) or severe joint deformity. Nail abnormalities and eye problems can also develop.

Asymmetric

Asymmetric psoriatic arthritis is the most common form of the disease, accounting for more than half of all cases, according to research in the Archives of Rheumatology. It is called asymmetric but the arthritic joints are not mirrored on both sides of the body. For example, one knee or wrist might be affected, but the other knee or wrist would not.

Asymmetric psoriatic arthritis, also known as oligoarticular psoriatic arthritis, is milder than its symmetrical counterpart in that no more than five joints are affected.

The larger joints will generally be affected, though the hand and foot may also be involved. Asymmetric psoriatic arthritis can often precede symmetric psoriatic arthritis but not always. Even though psoriatic arthritis affects women and men equally, men tend to have an 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 can lead to confusion in diagnosis. Rheumatoid arthritis differs in that it is characterized by a direct autoimmune assault on joint tissues. By contrast, psoriatic arthritis is caused by the "spill-over" of inflammation from psoriasis.

Symmetric psoriatic arthritis tends to affect women more than men. No one is quite sure why this is, but it is believed that hormones and menopause play a part.

Symptoms can range from mild to severe but are generally more severe than asymmetric psoriatic arthritis (in part because more joints are affected). In fact, around half of all people affected will experience some degree of disability as a result of symmetric psoriatic arthritis.

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

Diagnosis

There are no blood tests or imaging studies that can definitively diagnose psoriatic arthritis. The diagnosis is made primarily on a review of your physical symptoms and medical history. Imaging tests, such as X-ray and magnetic resonance imaging (MRI), play a key role in characterizing the nature and pattern of joint involvement.

If the cause remains uncertain, other procedures, such as needle aspiration or biopsy, may be used to evaluate joint fluid or tissues.

A rheumatologist will be able to cull the evidence to support the diagnosis. Example include the presence of skin lesions, nail deformity, or eye problems or the cyclic flare of symptoms common with all autoimmune disorders. A family history also plays a role in that you have a 50/50 chance of developing psoriatic arthritis if both of your parents have the disease.

As part of the diagnostic process, the rheumatologist will differentiate psoriatic arthritis from other diseases with similar symptoms. This includes rheumatoid arthritis, which can be diagnosed with the rheumatoid factor (RF) blood test, and gout, which can be differentiated by the presence of crystals in joint fluid.

Treatment

The treatment of asymmetric or symmetric psoriasis 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.

While symmetrical psoriatic arthritis tends to be more severe, the course of treatment is ultimately based on your pain, mobility, level of disability, quality of life, and associated medical conditions.

Treatment options include:

Severe cases may require surgery to either improve joint function (such as arthroscopic debridement) or fuse joints to reduce pain (arthrodesis).

An effort would also be made to identify your triggers for the disease so that you can avoid flares. One such example is stress. By better managing stress, such as with mind-body therapies like guided imagery or progressive muscle relaxation (PMR), you may be able to significantly reduce the recurrent of acute flares.

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