An Overview of Asymmetric vs. Symmetric Psoriatic Arthritis

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There are distinct patterns of joint involvement in people with psoriatic arthritis (PsA). Researchers have used these patterns to classify different types of PsA, with asymmetric oligoarticular (asymmetric PsA) and symmetric polyarthritis (symmetric PsA) being the most common.

Distal interphalangeal predominant, spondylitis, and arthritis mutilans are the three remaining known types of PsA that are less common than asymmetric and symmetric.

What Is PsA?

Up to 40 percent of people with psoriasis will go on to develop psoriatic arthritis, an inflammatory type of arthritis. Psoriasis is an inflammatory skin disorder that causes the skin to be itchy and scaly and nails to crumble.

Like psoriasis, PsA is an inflammatory disease, meaning it is a condition where inflammation, a normal response to infection and injury, occurs abnormally in healthy tissues, damaging them. With PsA, the abnormal inflammation occurs in the skin and joints. This inflammation triggers joint pain, swelling and stiffness, and skin rashes. Ongoing inflammation leads to joint and tissue damage, especially if PsA is not treated early and aggressively.

Most people with PsA experience both skin and joint symptoms. However, there are rare cases of PsA where skin symptoms are not experienced.

PsA symptoms vary from person to person. For example, some people may experience stiffness, pain, and inflammation in both hands and both feet while others may have significant back pain and mild symptoms in other joints.

Asymmetric PsA

Asymmetric PsA is the most common type of PsA, affecting more than half of people with PsA, according to research reported in the Archives of Rheumatology. It is called "asymmetric" because it does not affect the joints symmetrically. That means that one joint on one side is affected but the other one on the other side is not. For example, one knee or hand would be affected but the other knee or hand would not.

Asymmetric PsA will affect no more than five joints. Generally, it is the larger joints most affected by this type of PsA. There may also be hand and foot involvement. This type of PsA appears to be more prevalent in men, with a reported frequency of 30–40 percent.

Symmetric PsA

Symmetric PsA is similar to the autoimmune disease rheumatoid arthritis (RA). Both PsA and RA cause joint pain and stiffness, but RA does not cause the skin symptoms that PsA does. Symmetric PsA is milder than RA and will, therefore, causes less deformity and joint damage.

Symmetric PsA will affect joints on both sides of the body at the same time, which is similar to RA. For example, both hips or both knees are affected at the same time. This also means more than one joint will be affected at a time by PsA.

Symmetric PsA seems to affect more women than men, although PsA generally affects men and women equally. There are specific symptoms that distinguish symmetric psoriatic arthritis. One of these symptoms is thick, discolored, and pitted nails. Another classic sign of symmetric PsA is joint stiffness in the morning. Symmetric PsA may also affect larger joints, including the hips and knees.

Changing Patterns

Sometimes, people with PsA start with only a few affected joints, as is the cause with asymmetric PsA. Later on, their condition will affect many joints on both sides (symmetric PsA). Even with effective treatment, some people with asymmetric PsA will eventually develop symmetric PsA. 

There has been little research dedicated to addressing the clinical presentation of PsA. However, one older study going back 15 years found that of 129 early PsA patients with either symmetric PsA or asymmetric, 60 percent had symmetric PsA and 40 percent had asymmetric PsA.

Treatment

PsA affects both the inside and the outside of the human body. 

Regardless of the type of PsA a person has, the main goal of treatment is to control inflammation in order to ease pain and prevent joint and tissue damage.

There are medications to manage PsA, but when they don’t work and joint damage is prevalent, surgery is considered. The types of treatments prescribed are dependent on how severe PsA symptoms are. It may take more than one treatment to figure out what works to treat symptoms and prevent inflammation.

A Word From Verywell

Psoriatic arthritis has no cure. Treatment has to be as aggressive as the disease itself. Asymmetric PsA tends to be the least severe type, while symmetric PsA tends to be less severe than the remaining three types. It is possible for the type of PsA to change, becoming either worse or better with time.

Regardless of the type of PsA a person has, treatment needs to help with pain and other symptoms, and slow down the progression of the disease. It is, therefore, important for every person to learn how their body reacts to PsA and how to make the best use of their treatments for managing their disease.

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