What Are the Causes of Psoriatic Arthritis?

Medically Reviewed by David Zelman, MD on June 30, 2023
4 min read

Doctors don’t know exactly what causes psoriatic arthritis. But there are risk factors that make you more likely to get it.

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 trigger flare-ups of symptoms. You can try to avoid your triggers once you learn what they are. But while you do have the power to manage the condition, you aren’t to blame for having it in the first place. You didn’t cause this condition.

Although the cause of psoriatic arthritis isn’t known, there are things that make it more likely. These are called risk factors. Triggers are things that can set off a flare-up of the condition once you already have it.

Many things that put you at risk for psoriatic arthritis are beyond your control. These include:

Genes. Psoriatic arthritis can run in families. About 40% of people with this condition have a brother, sister, parent, or other family member who has psoriasis or arthritis. But that means roughly 60% of people with psoriatic arthritis don’t have a close relative with the condition.

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. These are both a risk factor for developing psoriatic arthritis and a potential trigger for a flare-up of it.

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. A bout of strep throat or other upper respiratory infection can lead to a flare-up of symptoms.

The HIV virus could also be involved. Psoriatic arthritis is more common in people who are HIV-positive.

A bout of strep throat or other upper respiratory infection can lead to a flare-up of symptoms.

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.

Severe psoriasis. Most people with psoriasis don’t develop psoriatic arthritis, but about 30% do. It’s not common, but some people who get psoriatic arthritis don’t have psoriasis symptoms. They may develop them later.

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

Age doesn’t seem to be a risk factor. Most people get psoriatic arthritis in their 30s, 40s, or 50s, but it can start at any age. And it doesn’t become more likely later in life.

Likewise, gender isn’t a risk factor for psoriatic arthritis.

You do have some power to curb other risk factors and triggers, including:

Sunburn or other skin injury. Wear sunscreen with an SPF of 30 daily. Sunburn 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. Too much stress for too long sends stress chemicals in your system.

Everyone has stress. It’s important to find healthy ways to manage it, such as exercise and meditation. Also, look for different ways to think about or handle the things that cause you stress. Working with a counselor or taking a stress management class can help with this.

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.

Obesity. Inflammation may be the link between psoriatic arthritis and obesity.

Keeping a diary can help you pinpoint what sets off psoriatic arthritis flare-ups. 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.