Better Markers Needed for SSc Patients with Rheumatoid Arthritis Overlap Syndrome, Study Says

Although serological markers correlate with joint inflammation in patients with systemic sclerosis (SSc), markers that might accurately diagnose systemic sclerosis-rheumatoid arthritis (SSc-RA) overlap syndrome are still lacking, a new study reports.

“Anti-CCP antibodies and rheumatoid factor in systemic sclerosis: Prevalence and relationships with joint manifestations” was recently published in the journal Advances in Clinical and Experimental Medicine.

Arthralgia (joint pain) due to inflammation is common in patients with SSc. However, the development of SSc-RA overlap syndrome is rare, and often hard to diagnose.

Two common measures of inflammation to diagnose RA are anti-citrullinated protein (a-CPP) antibodies and immunoglobin M class (IgM) rheumatoid factor (RF). These antibodies can also be present in SSc patients, especially those with joint involvement.

Researchers assessed these markers in a group of 100 Caucasian patients with SSc in Europe, and the potential relation between the markers and joint inflammation and arthritis.

Most of the SSc patients analyzed were women (82%), and most reported joint pain (90%) — 34% had arthritis and 24% reported joint contractures, in which joints can no longer bend properly. SSc-RA overlap syndrome was found in 6% of the patients.

There were no significant differences in IgM RF levels among SSc patients with or without arthritis. However, among the 46 people without arthritis but positive for IgM RF presence, most suffered from joint pain (91%).  The team therefore reported a significant correlation between joint pain and levels of IgM RF.

Levels of the a-CPP antibodies did not significantly correlate with the presence of joint pain or other joint manifestations. However, higher levels of this marker were seen in patients with arthritis (14%) compared to those without it (5%), suggesting that the levels of a-CPP antibodies significantly correlate with the presence of arthritis.

“The prevalence of RF and a-CCP antibodies is relatively high in SSc, and joint involvement occurs frequently,” the researchers concluded, adding that “arthritis is connected with the presence of a-CCP antibodies, while arthralgia [joint pain] is connected with the presence of IgM RF.”

Despite the connections seen between IgM RF and joint pain and a-CCP and arthritis, these markers cannot diagnose SSc-RA overlap syndrome, as they are not exclusive to this patient population, the researchers said. They emphasized that better serological markers to predict severe joint pain and arthritis are still needed.