Background OBJECTIVE: Estimate the frequency of the association of SLE with other autoimmune diseases in a large Spanish cohort of patients with systemic lupus erythematosus (SLE) and investigate the main risk factors for polyatoimmunity.
Methods Design: RELESSER is a nationwide multicentre, hospital-based registry of SLE patients. This is a cross-sectional study. Patients: Unselected consecutive adult patients with SLE, classified according to the American College of Rheumatology (ACR) 1997 criteria. All patients had been attended upon and followed at Spanish rheumatology departments. The first patient was enrolled in October 2011 and the last in August 2012. Main outcome: Polyautoimmunity was defined as patients who fulfilled criteria for SLE and other autoimmune disease: (1) autoimmune thyroiditis (alteration of thyroid function with the presence of anti-thyroid autoantibodies), (2) other connective tissue disease (rheumatoid arthritis, systemic sclerosis or inflammatory myopathy) and (3) mixed connective tissue disease. Multiple autoimmune syndrome (MAS) was defined as patients who meet SLE criteria and at least two other autoimmune diseases. Other variables: Demographic and clinical variables, Sjogren’s syndrome, antiphospholipid syndrome and family history of autoimmune systemic disease were collected. Statistical analysis: Descriptive, Chi-square test and ANOVA or Kruskal-Wallis for comparison between groups of patients. Multiple logistic regression analysis was performed to investigate the possible risk factors for polyautoimmunity in patients with SLE.
Results From all patients included in the registry, 3679 (91.4%) patients met 4 or more SLE criteria. Of these, 501 (13.6%) patients had Polyautoimmunity. The characteristics of this group are showed in table 1. The most frequent polyautoimmunity types associated with SLE were (in descending order over the total cohort of patients with SLE): autoimmune thyroiditis (7.5%), other connective tissue disorders (4.4%) and mixed connective tissue disease (2.7%). The percentage of patients a family history of SLE was 12.4%.
Multiple autoimmune syndrome was observed in 10.2% of patients with Polyautoimmunity. The multivariate analysis identified age (odds ratio [95% confidence interval], 1.01 [1.00–1.02]), sex (3.00 [1.48–6.04]), Raynaud’s phenomenon (1.79 [1.34–2.39]), pulmonary fibrosis (2.88 [1.32–6.30]), Ro-La autoantibodies (1.68 [1.20–2.36]), antiRNP (1.79 [1.32–2.42]) and treatment with methotrexate (1.54 [1.08–2.18]) or with antimalarials (0.57 [0.41–0.78]) as factors associated with polyautoimmunity.
Conclusions SLE patients frequently associate other autoimmune diseases, detecting poliautoimmunity in 14%, MAS in 2%, family history of SLE in 12.4% and others such as Sjogren’s syndrome and secondary SAF in 12.8% and 12.7% respectively. More studies are needed to better understand the increase of polyautoimmunity that seems to be observed in SLE.
Funding Source(s): None
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