Clinical features may distinguish causes in primary Sjögren’s joint pain
Accurate distinction of osteoarthritis and inflammatory arthritis key for treatment
Osteoarthritis, rather than inflammatory arthritis, was the more common cause of joint pain among primary Sjögren’s syndrome patients in a small study.
While arthritis is associated primarily with inflammation and swelling, osteoarthritis (OA) typically is linked to the mechanical wearing down of joints.
Analyses revealed that older age and certain metabolic features, including elevations in the levels of some fatty molecules and waste products, were associated with OA, whereas greater disease severity and organ involvement were linked to arthritis.
“In the future, it may be necessary to be more cautious in the diagnosis of joint manifestations in [Sjögren’s] patients in order to make the appropriate treatments,” the researchers wrote.
The study, “Osteoarthritis or arthritis? Toward understanding of primary Sjögren’s syndrome patients with arthralgia,” was published in the Journal of Orthopaedic Surgery and Research.
In Sjögren’s syndrome, the immune system mistakenly launches an attack on the body’s own tissues. While moisture-producing glands are the primary targets of this misdirected attack, other tissues in the body can be affected.
The joints are a common site of damage in Sjögren’s. Patients sometimes experience arthritis, or joint inflammation and swelling, that can lead to significant joint pain.
Another major cause of joint pain, particularly in elderly people, is OA, which is also called degenerative joint disease. In contrast to inflammatory arthritis, joint pain in OA is primarily driven by mechanical wear-and-tear that occurs when the cartilage within a joint starts breaking down.
Recent evidence suggests that Sjögren’s patients also may be at an increased risk for OA. It might, therefore, be difficult to determine the cause of joint pain in Sjögren’s, the researchers noted.
The team conducted a study to learn more about the clinical features associated with OA and inflammatory arthritis in 368 people with primary Sjögren’s who were seen at a hospital in China between March 2010 and December 2020.
Among them, 186 had OA and 41 had inflammatory arthritis. Almost half of the people with OA had involvement of multiple joints, most often the knee and spine. Arthritis predominately affected joints in the fingers and hands.
OA was associated with a higher likelihood of being 65 or older, having more joint involvement, and a longer disease duration.
Assessment tools: EULAR and ESSDAI
Still, OA patients generally had less severe disease, as assessed by the European Alliance of Associations for Rheumatology (EULAR) Sjögren’s syndrome disease activity index (ESSDAI).
OA also was associated with metabolic changes, including higher blood levels of cholesterol, a type of fat, and uric acid, a waste product, compared with people who didn’t have OA.
Ultimately, being 65 or older and having joint pain were found to be significant predictors of OA, raising the risk by about 2 and 3.4 times, respectively.
“The older the [ Sjögren’s] patient with joint pain and the longer the course of disease, the more likely it was to be combined with OA,” the researchers wrote.
In contrast, inflammatory arthritis was associated with higher median ESSDAI scores, as well as a higher frequency of muscle involvement, joint pain, and swollen salivary glands.
Among all Sjögren’s patients who presented with joint pain, 12 were determined to have arthritis only and 84 had solely OA. Those with OA were significantly older, while those with arthritis had significantly higher ESSDAI scores and involvement of other organ systems.
OA patients also had metabolic alterations, including higher levels of uric acid and triglycerides (a type of fat) in the bloodstream.
Overall, for Sjögren’s patients with arthritis, “the disease symptoms and immunological characteristics of itself are more prominent,” the researchers wrote, adding that with OA, “metabolic abnormalities are more obvious.”
Being able to distinguish the two conditions, “has important implications for treatment options,” the researchers noted. For example, while hydroxychloroquine or other immunosuppressants may help to ease arthritis, several of these medications aren’t recommended for OA.
Additional research is needed to identify “long-term outcomes of initial arthralgia,” and to “explore the mechanisms by which arthralgia progresses to arthritis or OA,” the team wrote.
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