Autoantibody Associations in Systemic Sclerosis Save

Analysis of two large cohorts of systemic sclerosis (SSc) patients shows a signfiicant minority of patients to have autoantibodies typical of rheumatoid erosive arthrits, but their presence in SSc patients was associated with unique manifestations of SSc. 

Overall 448 SSC patiens were enrolled from the EUSTAR (French) cohorts between 2015 and 2019.  Lab results for IgM rheumatoid factor (RF), IgG anti-citrullinated proteins (ACPA) and IgG anti‐carbamylated proteins antibodies (anti-CarP) from a central laboratory were correlated with clinical manifestations.

Seropositivity was often found in these SSC patients:

• 25% RF+
• 9%  ACPA+
• 14% CarP+

By multivariate regression analysis, patients seropositive for RF and ACPA were more likely to have RA overlap disease (OR 5.7, 95% CI 2.3-13.8 and OR 44.1, 95% CI 15.4-126.3, respectively).

ACPA positivity was significantly linked to synovitis/ tenosynovitis (OR 1.7, 95% CI 1.0-2.6).

Major vascular complications were more likely in those who were RF positive (OR 2.1, 95% CI 1.3-3.4).

Those with anti-CarP antibodies were more likely to have digital ulcers (OR 1.9, 95% CI 1.1-3.4) and fibrotic skin and lung disease (OR 2.0, 95% CI 1.1-3.6).

Typical RA autoantibodies were often associated with RA overlap, synovitis, tenosynovitis, digital ulcers and fibrotic skin and lung disease.