What Causes Psoriatic Arthritis?

Psoriatic arthritis (PsA) is an autoimmune disease that targets the joints, leading to inflammation, pain, and swelling. PsA usually affects people with pre-existing psoriasis—a chronic skin condition that causes raised and discolored patches, called "plaques."

PsA occurs as a result of a disruption in the immune system, which causes your body to attack healthy cells in your joints and skin by mistake. Why a dysfunction in your immune system occurs is currently known. The National Institute of Arthritis and Musculoskeletal and Skin Diseases explains that the cause of most autoimmune diseases is unknown and research remains ongoing.

That said, research shows that a combination of medical, genetic factors, and environmental factors can increase your risk of developing PsA.

Pre-existing Psoriasis

According to a systematic review and meta-analysis of 266 studies, researchers found 25% to 30% of all people with psoriasis eventually develop PsA. Those who have moderate-to-severe psoriasis are at a higher risk for PsA compared to people with mild psoriasis.

It’s also important to note that people who have had psoriasis for a longer period of time are more likely to develop PsA. Studies show that it takes an average of 10 years for someone to get PsA after they’ve been diagnosed with psoriasis.  ​

Genetics

Genetic research for PsA is still underway. Some studies have shown that around 33% to 50% of people with PsA have at least one immediate relative who also has the disease.

Researchers have also been able to identify some of the genes that people with PsA have in common. The exact role of these genes is still being studied, however. 

People born with human leukocyte antigen (HLA) genes, such HLA-B and HLA-C can be more likely to develop the condition. HLA genes play a role in producing proteins that help your immune system identify the difference between healthy and harmful cells.

Having these genes doesn't guarantee that you will develop PsA in your lifetime. Generally, your risk for PsA increases if your genetics are combined with environmental risk factors. 

Environmental Factors

Environmental risk factors encompass lifestyle habits, stressors, traumatic events, and injuries or infections. While having these risk factors doesn’t automatically mean you can get PsA, you can be more at risk for developing symptoms if environmental stimuli are combined with medical and genetic factors. 

Common environmental risk factors may include: 

• Obesity: The correlation between obesity and PsA is still being researched. However, some studies show that obesity can raise your level of cytokine—the proteins in your body that produce inflammation in your joints.
• Injury: A 2021 review found that people who experienced previous injury or trauma to the joints and bones and have psoriasis may be at an increased risk of developing PsA symptoms.
• Illness: The way your body responds to viral or bacterial infections can trigger an overactive immune system response. Studies show that infections like strep throat and HIV can affect the functioning of your T-cells—white blood cells in your immune system that help your body fight illnesses.
• Tobacco and alcohol use: Some evidence suggests that smoking and drinking alcohol excessively can worsen inflammation and increase your risk of PsA, especially if you have pre-existing psoriasis. Research between these lifestyle habits and PsA is ongoing.

Who Can Get Psoriatic Arthritis?

PsA is a condition that generally affects people with pre-existing psoriasis. In fact, studies show that up to 85% of people with PsA have a history of psoriasis.

But in some cases, other factors can contribute to your risk of developing symptoms. These factors include:

• Age: Although you can develop PsA at any age, adults between the ages of 30-50 most often receive a diagnosis.
• Sex: Some conditions can be more prevalent based on your assigned sex at birth. With PsA, however, males and females are equally likely to receive a PsA diagnosis. But, women are less likely to achieve remission. Researchers suggest that fluctuating hormone levels and the inflammatory effects of estrogen may be to blame. 
• Ethnicity: White people receive a PsA diagnosis at higher rates than people who are Black, Asian, or Latino. However, this does not mean that Black, Asian, and Latino people are at a reduced risk of developing PsA—it means they are less likely to have a PsA diagnosis. Studies suggest that the lack of research participants with darker skin tones in PsA studies and racial disparities in access to care may explain the lower prevalence rates. 

A Quick Review

Psoriatic arthritis is an inflammatory autoimmune condition that affects the joints, commonly occurring in people who have pre-existing psoriasis. Like other autoimmune diseases, people with PsA have a dysfunction in their immune system that causes their body to attack healthy joint and skin cells. 

The exact cause of PsA remains unknown while research remains ongoing. However, a combination of pre-existing psoriasis and other genetic and environmental factors can increase your risk of developing symptoms. 

If you think you may be at risk for developing PsA or have pre-existing psoriasis and recent changes in your joint health or mobility, you may consider reaching out to your healthcare provider for proper testing. Getting tested can get you a diagnosis sooner and get started on the right treatment options for you.