To assess the prevalence and potential associations with the systemic sclerosis (SSc) phenotype of additional autoimmune diseases (AID).
A multicenter study was performed in France and Italy to recruit consecutive European Caucasian patients with SSc systematically assessed for the coexistence of predefined AID known to occur with connective tissue diseases.
We recruited 585 French and 547 Italian patients with SSc. Specific AID were found in 114/585 (19%) French and 179/547 (33%) Italians with SSc (p < 0.0001). Sjögren's syndrome and thyroiditis were the predominant AID in both cohorts (12% for Sjögren's syndrome and 6% for thyroiditis in the combined populations). The frequency of myositis, primary biliary cirrhosis, rheumatoid arthritis, and systemic lupus erythematosus was low (< 4%) and similar in both cohorts. The coexistence of at least 1 of the AID in the whole cohort was associated in multivariate analysis with the limited cutaneous subtype, the presence of antinuclear antibodies, and a lower prevalence of digital ulcers.
Our study shows that 21% of this large series of European Caucasian patients with SSc have developed at least 1 AID. This latter condition identified a subset of patients with milder disease. Thus, associations of AID and autoimmune background in SSc have to be considered for further therapeutic and biological investigations in SSc.