What Are the Causes of Psoriatic Arthritis?

In psoriatic arthritis, the immune system goes haywire and turns against the skin and joints. Its attack leaves behind scaly patches and swollen, sore joints.

It's not clear what sets off this immune attack. Researchers think a combination of genes and infections or other environmental factors may be to blame.

Once you have psoriatic arthritis, triggers like stress, certain medicines, and injuries can set off bouts of symptom flares. You can try to avoid your triggers once you learn what they are.

Psoriatic Arthritis Causes

Genes. Psoriatic arthritis runs in families. About 40% of people with this condition have a brother, sister, parent, or other family member who has psoriasis or arthritis.

Shared genes are the common link. A group of genes called HLA help the immune system tell its own proteins from foreign ones. Changes to HLA genes could lead to psoriatic arthritis by making it harder for the immune system to know when it's attacking its own cells.

Other genes could also be involved. So far, researchers have found more than two dozen gene changes that make people more likely to get psoriasis and psoriatic arthritis.

Genes only set the stage for psoriatic arthritis. A virus or something else in the environment triggers the disease.

Infections. Some people get psoriatic arthritis after an infection, but it's not clear which bacteria or viruses are to blame. The strep bacteria that cause sore throats could be one. The HIV virus could also be involved. Psoriatic arthritis is more common in people who are HIV-positive.

Injuries. A new plaque sometimes forms on the skin after a cut, scratch, or other injury. The joint closest to the injured area might also swell up. Doctors call this the Koebner phenomenon.

No one knows exactly how skin damage leads to plaques, but it's likely due to the immune response. Natural chemicals that your immune system makes rush to the injury site to spur healing -- and that process brings on inflammation.

Flare Triggers

When you have psoriatic arthritis, you might find that certain things make your symptoms worse. Figuring out your triggers and avoiding them can help you prevent flare-ups.

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Sunburn or other skin injury. The red color your skin turns after you've been out in the sun too long is a sign of injury. Skin damage causes inflammation that can set off psoriatic arthritis symptoms. This is the Koebner phenomenon at work. Cuts, scrapes, and other skin injuries can also lead to a flare.

Stress. Inflammation is also part of your body's response to stress. Being under constant tension releases a barrage of stress chemicals in your system.

Infection. Infection is both a psoriatic arthritis risk and a trigger. A bout of strep throat or other upper respiratory infection can lead to a flare-up of symptoms.

Medicines. Some drugs you take to treat other conditions can make your psoriatic arthritis worse. These include:

Alcohol. Alcohol promotes joint inflammation. Drinking too much might worsen psoriatic arthritis symptoms. Some people with psoriatic arthritis claim that their symptoms improve when they avoid alcohol.

Cigarettes. Smoking both raises the risk for psoriasis and makes the disease worse. Exactly how cigarettes affect psoriatic arthritis isn't as clear. There is some evidence that people who smoke don't respond as well to their psoriatic arthritis medicine as nonsmokers.

Food: Foods like these seem to trigger psoriatic arthritis flares in some people:

You may want to limit or avoid any foods that bother you. Instead, eat more foods that may improve psoriatic arthritis symptoms, like fruits, vegetables, and fish oil. If you’re not sure which foods may be a problem, keep notes on what you eat and what symptoms you have and share it with your doctor, who may recommend that you take a break from those foods for a few weeks and add them back one at a time to see if it makes a difference. Your doctor may call this an elimination diet.

Finding Your Triggers

Keeping a diary can help you pinpoint your triggers. Write down when your symptoms get worse and what you were doing at the time. Also keep track of the foods you eat.

Share your diary with your doctor at each visit. Knowing your triggers and managing them will help you gain more control over your condition.

WebMD Medical Reference Reviewed by Debra Jaliman, MD on April 17, 2019

Sources

SOURCES:

American Academy of Rheumatology: "Psoriatic Arthritis."

Arthritis Foundation: "What Triggers an Arthritis Flare?"

Dermatology and Therapy: "Dietary behaviors in psoriasis: Patient-reported outcomes from a U.S. national survey."

DermNet NZ: "Koebner phenomenon."

Expert Review of Clinical Immunology: "The relationship between smoking, psoriasis and psoriatic arthritis."

National Psoriasis Foundation: "Causes and Triggers," "Genes and Psoriasis," "How cigarettes and alcohol affect psoriasis," "Stress and psoriatic disease."

Rheumatoid Arthritis Support Network: "PsA Management: How Can I Manage My Symptoms?"

UpToDate: "Patient education: Psoriatic arthritis (Beyond the Basics)."

U.S. National Library of Medicine: "Psoriatic arthritis."

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