What Causes Psoriatic Arthritis?

Psoriatic arthritis (PsA) can be hereditary, and the condition often runs in families. PsA occurs as a result of a disruption in the immune system, which causes the body to attack healthy cells in the joints and skin by mistake. The exact cause is unknown, but a combination of risk factors can make it more likely for a person to develop PsA.

PsA is an autoimmune disorder that targets the joints, leading to inflammation, pain, and swelling. The condition usually affects people with pre-existing psoriasis. This chronic skin condition causes raised and discolored patches called plaques.

Theories

The cause of most autoimmune disorders is unknown, and research is ongoing. Researchers have indicated that a combination of medical, genetic, and environmental factors can increase your risk of PsA.

Pre-Existing Psoriasis

A review and meta-analysis of 266 studies published in 2019 found that 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 important to note that people who have had psoriasis for longer are more likely to develop PsA than others. Research has shown that it takes an average of 10 years for a person to develop PsA after being diagnosed with psoriasis. Some people can also develop arthritis symptoms prior to PsA.​

Is Psoriatic Arthritis Hereditary?

PsA has a strong genetic component. Some evidence suggests that around 33% to 50% of people with PsA have at least one immediate family member with the condition. Research has also been able to identify some of the genes people with PsA have in common, but the exact role of these genes is unclear.

People born with variations of certain human leukocyte antigen (HLA) genes, such as HLA-B27, can be more likely to develop PsA. HLA genes produce proteins that help the immune system identify healthy and harmful cells.

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

Who Gets Psoriatic Arthritis?

PsA is a condition that generally affects people with pre-existing psoriasis. Research has shown that up to 85% of people with PsA have a history of psoriasis.

Other factors can contribute to your risk of developing symptoms, including:

• Age: You can develop PsA at any age, but adults aged 30–50 most often receive a diagnosis.
• Ethnicity: White people receive a PsA diagnosis at higher rates than people who are Black, Asian, or Latino. This does not mean that Black, Asian, and Latino people are at a reduced risk of PsA, but they are less likely to have a PsA diagnosis. The lack of research participants with darker skin tones in PsA studies and racial disparities in access to care may explain the low prevalence rates.
• Sex: Women and men are equally likely to receive a PsA diagnosis, but women are less likely to achieve remission. Research has shown that fluctuating hormone levels and the inflammatory effects of estrogen may play a role. 
  

Risk Factors

Environmental risk factors include lifestyle habits, stressors, traumatic events, and injuries or infections. Having these risk factors doesn't automatically mean you can get PsA. You can be more at risk if environmental stimuli are combined with medical and genetic factors. 

Illness and Injury

The way your body responds to viral or bacterial infections can trigger an overactive immune system response. Research has shown that infections like strep throat and human immunodeficiency virus (HIV) can affect the functioning of your T-cells. These white blood cells help fight illnesses. Injury or trauma to the joints and bones may also increase the risk of PsA in people with psoriasis.

Obesity

The link between obesity and PsA is unclear. Some evidence suggests that obesity may raise your level of cytokines. These proteins produce inflammation in your joints.

Tobacco and Alcohol Use

Research has shown that smoking and heavily drinking alcohol 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.

A Quick Review

The exact cause of PsA remains unknown, and research is ongoing. A combination of pre-existing psoriasis and other genetic and environmental factors can increase your risk.

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