People with psoriasis have an increased risk of developing psoriatic arthritis (PsA). New research shows that psoriasis severity and body surface area play a role in determining the extent of the risk.

Psoriasis is a chronic, autoimmune disease that affects the skin, causing dry, itchy patches with a covering of scales. In the United States, more than 7.5 million adults are living with this skin condition, which equates to about 3% of the adult population.

PsA is a chronic, inflammatory type of arthritis that leads to symptoms such as joint pain, stiffness, and swelling. Although it is possible to develop PsA without having psoriasis first, up to 34.7% of people living with psoriasis worldwide develop PsA.

The collective name for these two conditions is psoriatic disease. Researchers have looked into the link between these conditions and how they affect one another. Of particular interest are predictive symptoms that may indicate whether a person with psoriasis will also develop PsA.

More recently, researchers have looked at how the severity of psoriasis may affect the onset of PsA. A 2021 study showed a correlation between more severe cases of psoriasis and the development of PsA.

This article explores what experts know about the connections between psoriasis severity and PsA.

Over the years, researchers have studied the connection between psoriasis and PsA. Part of what they have looked for is trends in symptoms that may predict the likelihood that a person with psoriasis will develop PsA, as well.

As more than one-third of people living with psoriasis may also develop PsA, understanding what risk factors to look for may help doctors diagnose the joint condition sooner. The earlier diagnosis and treatment of PsA may lead to better outcomes and improved quality of life.

Symptoms as risk factors

In a 2009 study, researchers found that the presence of certain psoriasis symptoms may increase a person’s risk of developing PsA. The findings showed a link between the presence of the following psoriasis symptoms and an increased risk of PsA:

  • nail dystrophy
  • scalp lesions
  • intergluteal or perianal lesions

In another study from 2010, researchers shared similar results. They noted that the following psoriasis symptoms or factors were positively associated with an increased risk of developing PsA:

  • increased psoriasis severity
  • family history of psoriatic disease
  • personal history of morning stiffness, musculoskeletal pain, or fatigue
  • presence of scalp, intergluteal, or perianal psoriasis
  • nail dystrophy
  • dactylitis, which is swelling in the fingers or toes

Psoriasis severity and PsA risk

Research is beginning to show that the severity of a person’s psoriasis may indicate that they have an increased risk of developing PsA.

In one older study from 2010, researchers acknowledged that severe cases of psoriasis increased a person’s risk of developing PsA.

In a more recent 2021 study, researchers noted the same association. However, they cautioned that these findings might not be generalizable to the larger population.

In another 2021 study, researchers argued that the total body surface area that psoriasis covers may help predict the likelihood of developing PsA. The study authors also noted depression and obesity as additional risk factors.

The Global Healthy Living Foundation notes that although anyone living with psoriasis can develop PsA, psoriasis that covers a larger area of the body puts people at higher risk.

The organization also lists additional risk factors that could influence whether a person with psoriasis goes on to develop psoriatic arthritis. These factors include:

  • age
  • genetics and family history
  • environmental factors
  • obesity
  • smoking status

Growing evidence suggests that the severity of psoriasis symptoms, including the amount of the body that they affect, directly corresponds with the risk of developing psoriatic arthritis.

People who receive a diagnosis of psoriasis should talk with the doctor about their individual risk of developing PsA. They should also inform the doctor if they start to experience any joint symptoms that may indicate PsA.