Systemic sclerosis (SSc) is a complex systemic autoimmune disease with variable phenotype and prognosis. Autoantibodies are important diagnostic biomarkers in SSc. More than 90% of patients with SSc had anti-nuclear antibodies. Autoantibodies specific to SSc (anti-topoisomerase I antibodies, anti-centromeres, anti-RNA polymerase III, anti-Th/To, anti-fibrillarin, anti-NOR90) or associated with overlap syndromes (anti-RNA polymerase III antibodies -PM/Scl, anti-KU, anti-U1RNP, anti-TRIM21) are detected in most patients. Excluding anti-TRIM21 antibodies, autoantibodies are usually mutually exclusive and are associated with distinct phenotypes.

Around 5 to 10% of patients with SSc have no autoantibodies detectable with routine biological tests. Recently, new autoantibody specificities have been described in SSc (anti-eIF2B, anti-RuvBL1/2, anti-BICD2, anti-U11/U12 RNP antibodies).

"Seronegative" patients could represent new specificities of autoantibodies (unknown or not currently routinely evaluated) associated with different phenotypes of the disease.

Primary objective is to compare the phenotype of patients with systemic sclerosis with or without detectable specific or associated autoantibodies.

Secondary objectives are:

• to determine homogeneous groups of patients with systemic sclerosis without detectable specific or associated autoantibodies
• to compare the phenotype of patients with systemic sclerosis without detectable specific or associated autoantibodies according to anti-nuclear antibodies status

Inclusion Criteria:

• Patient with systemic sclerosis defined according to ACR/EULAR 2013 classification criteria
• Patient with a minimum follow-up of 3 years since the diagnosis of systemic sclerosis
• Patient evaluated for the following systemic sclerosis specific and/or associated autoantibodies: anti-topoisomerase I, anti-centromere, anti-RNA polymerase III (RP155 and RP11), anti-Th/To antibodies , anti-fibrillarin, anti-NOR90, anti-PM/Scl, anti-KU, anti-U1RNP and anti-SSA antibodies (independently of antinuclear antibodies status)

Exclusion Criteria:

• Patient with equivocal results for one or more systemic sclerosis specific and/or associated autoantibodies
• Patient initially negative but with a positive result for systemic sclerosis specific and/or associated autoantibodies during follow-up

Patients followed in internal medicine or rheumatology units until December 2021