Study Finds People With Psoriatic Arthritis Have Increased Risk for Lupus

A recent study published in The Journal of Rheumatology has explored the potential link between psoriatic arthritis (PsA) and lupus.¹

PsA often occurs alongside psoriasis, an inflammatory skin condition. However, in PsA, the joints are inflamed instead of the skin, causing arthritis. This leads to significant joint pain and swelling. Psoriatic arthritis, like psoriasis and lupus, is an autoimmune condition.

It is not uncommon for people with an autoimmune condition to develop other autoimmune conditions. However, not much is known about the potential link specifically between PsA and lupus.

How was the study designed?

The researchers reviewed the medical records of nearly 5,000 people with psoriatic arthritis. They also reviewed records from a control group. People in the control group had many similar features to those in the PsA group, like age, sex, and medicines are taken. However, people in the control group had not been diagnosed with PsA.¹

This allowed the researchers to compare those with PsA to similar people without the condition and look for differences. All records reviewed were from the years 2002 to 2017. There were more than 24,000 people in the control group.¹

What were the results?

Overall, 0.37 percent of the people in the PsA group also had lupus. In contrast, only 0.15 percent of those in the control group had lupus. Although these numbers seem small, they were quite significant.¹

These results suggest that those with PsA had a 2.3-fold increased risk of also having lupus compared to those without the condition. It was more common for women in the study to have both PsA and lupus. This makes sense, considering lupus affects women more often than men. It is thought that PsA impacts men and women relatively equally.¹

There were also some other trends in lupus risk within the PsA group. For example, the researchers found that the older a person was at the time of their PsA diagnosis, the higher their risk was of also having lupus. Also, shorter times since diagnosis increased lupus risk.¹

Additionally, those with PsA who were also taking statins (a type of drug often used to lower cholesterol) seemed to have a higher risk of developing lupus, too. The researchers also found that those in the PsA group had a greater chance of taking a medicine known to cause lupus (called drug-induced lupus).¹

What about other research?

Interestingly, there was another study published in 2016 that found similar trends between PsA and lupus. Overall, the researchers found that those with lupus had a greater chance of having PsA and/or psoriasis than the general population. About 5 percent of those with lupus also had psoriasis, and 4.5 percent had PsA. Both of these numbers are greater than the risk for the general population.²

Additionally, the researchers found that some lupus-related symptoms were more common in people with psoriasis or PsA than in those without either condition. Some of these symptoms included:²

• Malar rash (a red or purple rash on the cheeks and nose, also known as butterfly rash)
• Discoid rash (round lesions that usually appear on the scalp and face)
• Arthritis
• Sensitivity to light (photosensitivity)

Why might there be a connection?

It is unclear why there may be a connection between lupus and PsA; however, the researchers proposed a few theories. They suggested that those with PsA may have more co-occurring medical conditions and be taking a higher number of medicines known to cause lupus.¹

It may also be possible that some treatments used for PsA, like phototherapy or certain drugs, may also lead to the development of lupus. Finally, they suggest that the underlying cause of both conditions may be similar, potentially involving the same specific inflammation-causing cells.¹

Overall, the researchers concluded there is an increased risk of having lupus if a person also has PsA. These results may impact drug or treatment choices for those at risk and will help provide further insight into both of these conditions. Although these findings are interesting, much more research is needed to better understand this potential link.