Sjögren’s syndrome secondary to systemic lupus erythematosus rises in frequency with age, affects nearly one-quarter of all people with SLE, and is marked by a systemic inflammatory state with high levels of proinflammatory cytokines.
Those are key findings from a Swedish study that set out to evaluate the subjective and objective symptoms of secondary Sjögren’s syndrome (sSS) from a large cohort of SLE patients and matched controls.
“The diagnosis SS is a clinical entity, based on dryness of eyes and mouth due to destructive inflammation in the exocrine glands, especially tear and salivary glands,” researchers led by Guillermo Ruacho, DMD, and Marika Kvarnström, MD, PhD, of the Karolinska Institute, wrote in a study published in the Journal of Rheumatology (doi: 10.3899/jrheum.190250). “SS can exist [as] isolated, primary SS (pSS) or together with other rheumatic diseases, referred to as secondary SS (sSS). A major difference according to the 2002 Revised American-European Consensus Criteria (AECC) is the classification where the serologic item (SSA/SSB antibodies) is included for pSS, but not for sSS (Ann Rheum Dis. 2002;61:554-8). In SLE, these autoantibodies are common, usually stable over time, and they appear early, even several years before disease onset.”
The researchers evaluated 504 consecutive SLE patients and 319 controls from the general population, who were matched for age and gender to the first 319 SLE patients. They used AECC to define SLE-sSS and conducted a thorough clinical investigation of all patients, including analysis of autoantibodies and 20 selected cytokines.
The researchers found that SLE-sSS occurred in 23% of the SLE patients. In comparison with SLE patients who did not have sSS, those in the SLE-sSS group were an average of 9 years older, more likely to be female (96% vs. 84%, respectively), and more likely to have leukopenia (57% vs. 45%), yet less likely to have nephritis (32% vs. 43%). Of 20 proinflammatory cytokines investigated, 6 were higher in the SLE-sSS group: TNF-alpha, IL-6, MCP-4, MIP-1beta, IL-12/IL-23p40, and IP-10. Other clinical measures higher in the SLE-sSS group were total IgG, anti-SSA/Ro52, anti-SSA/Ro60, anti-SSB/La antibodies, and rheumatoid factor (IgM and IgA; P less than .05 for all comparisons).
“To our knowledge this is the first study to investigate if systemic inflammation, as measured by cytokine levels, differs between SLE-sSS and SLE-nonsSS,” the researchers wrote. “In clinical practice, it is often difficult to delineate pSS from SLE-sSS. Organ manifestations commonly reported in pSS are fever, lymphadenopathy, parotid gland enlargement, Raynaud’s phenomenon, interstitial lung disease, peripheral neuropathy, and vasculitis. All these clinical features, except parotid gland enlargement, were investigated in the present study, but only peripheral neuropathy differed and was more frequent in SLE-sSS than in SLE-nonsSS.”
They acknowledged certain limitations of the study, including the fact that they did not measure saliva and tear production in controls without sicca symptoms.
The study was supported by funds from Swedish local and national governments, medical societies, foundations, and patient advocacy groups, One author is an employee at AstraZeneca, which provided reagents for the cytokine analyses but had no impact on the analyses, the authors said.
SOURCE: Ruacho G et al. J Rheumatol. 2019 Sep 1. doi: 10.3899/jrheum.190250.