People with early-onset primary Sjögren's syndrome may have more severe disease that worsens over time, according to a study published online December 17 in Rheumatology.
The results suggest that Sjögren's syndrome that is diagnosed at age 35 years or younger is associated with specific symptoms that may predict severe systemic disease.
"Our data suggest the existence of a specific phenotype, corresponding to early-onset disease, with particular clinical and biological characteristics. These features have been described previously as predictive factors of severe systemic disease and development of lymphoproliferative disease," write Celine Anquetil, MD, of CHU Claude Huriez, Lille Cedex, France, and colleagues.
The researchers analyzed data from 393 adults with primary Sjögren's syndrome who were recruited between 2006 and 2009 into the Assessment of Systemic Signs and Evolution in Sjögren's Syndrome (ASSESS) study. The ASSESS study was a prospective, nationwide French study that sought to identify factors predictive of systemic involvement in primary Sjögren's syndrome. The study included 55 patients diagnosed with early-onset Sjögren's syndrome (aged 35 years or younger) and 338 individuals with later-onset disease.
The investigators compared clinical and biological symptoms at baseline and at 5 years after diagnosis. They used the European League Against Rheumatism Sjögren's Syndrome Disease Activity Index (ESSDAI) to measure disease activity.
The analysis compared the early-onset group with the later-onset one and found several clinical factors associated with early-onset disease. These factors also suggested that early-onset disease was more severe and that it was characterized by systemic involvement. In comparison with later-onset disease, in early-onset Sjögren's, there was a higher prevalence of salivary gland enlargement (47.2% vs 33.3%; P = .045), swollen lymph nodes (25.5% vs 11.8%; P = .006), purpura (23.6% vs 9.2%; P = .002), and renal involvement (16.4% vs 4.4%; P = .003).
Immune factors associated with early-onset as compared with later-onset disease included hypergammaglobulinemia (60.8% vs 26.6%; P < .001) and lower levels of complement component 3 (C3) (18.9% vs 9.1%; P = .032) and complement component 4 (C4) (54.7% vs 40.2%; P = 0.048). Both C3 and C4 play a role in innate immunity and help distinguish self-antigens from foreign antigens.
Autoantibodies associated with early-onset vs later-onset Sjögren's syndrome included rheumatoid factor positivity (41.5% vs 20.2%, P < .001), anti–Sjögren's syndrome–related antigen A (anti-SSA) (84.6% vs 54.4%; P < .001), and anti-SSB (57.7% vs 29.7%; P < .001).
The early-onset group also showed a change in ESSDAI scores that suggested a trend toward worsening of disease 5 years after diagnosis (0.72; P = .27). In contrast, the later-onset group showed significant improvement (-1.27; P < .0001).
Rates of lymphoma were similar for the the early-onset and later-onset groups (3.6% vs 4.7%; P = 1).
Although having Sjögren's syndrome typically does not increase the risk for death relative to the general population, about 15% of affected individuals may develop serious complications, including lymphoma. The results from this study highlight the importance of careful follow-up for patients diagnosed with Sjögren's syndrome, in order to identify those individuals with systemic complications.
Sjögren's syndrome is an autoimmune disorder that typically starts between ages 40 and 60 years. It usually presents with sicca syndrome, which affects the exocrine glands and causes dry mouth and dry eyes. However, the condition can have a wide range of manifestations, including neurologic, renal, and pulmonary symptoms. Past studies, as well as a recent meta-analysis, have suggested that early-onset disease may be linked to more severe systemic disease.
The authors note that the small size of the early-onset group and the small number of disease-related events could have affected the ability to find statistically significant differences between the two groups. Also, the 5-year follow-up may have been too short for conditions such as lymphoma to develop. They are planning a 20-year follow-up study, which may answer more questions.
They point out that the results seem to confirm findings from other studies suggesting that early-onset Sjögren's may have specific, measurable features that may help predict prognosis and risk for early mortality.
"Even if further studies are needed to confirm these results, age at disease onset can help us to identify patients at increased risk of severe primary Sjögren's syndrome and requiring closer follow-up," the authors conclude.
The study was supported by grants from the French Ministry of Health (Programme Hospitalier de Recherche Clinique) and the French Society of Rheumatology. The authors have disclosed no relevant financial relationships.
Rheumatology. Published online December 17, 2018. Abstract
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