Ethnic influence on the phenotype of French patients with systemic sclerosis

Systemic sclerosis (SSc) is a rare multisystem autoimmune disorder. It has a worldwide distribution but geographical and ethnic influences are poorly known.

The aim of the study was to compare demographic characteristics and frequency of internal organ system involvement of Black SSc patients to those of White SSc patients in France. Patient population included 425 SSc patients recruited at Cochin Hospital in Internal medicine and Rheumatology departments. Data were collected at the baseline visit, each Black patient was matched with 2 to 3 White controls from the same department.

One hundred and five Black patients and 320 White were included. Demographic comparison highlighted an older age for the White patients (48.66±14.87 vs 39.56±10.79, P<0.0001). Phenotypic comparison showed more severe skin involvement for Black patients: they had more often diffuse skin involvement than White patients (69.2% vs. 44.7%, P<0.0001) with a higher baseline modified Rodnan skin score (15.8 vs. 11.3, P<0.001). Comparisons also showed more active ulcers (46.5% vs. 21.6%, P<0.001) and more common interstitial lung disease (73.7% vs. 43%, P<0.0001) for Black patients. Auto-antibody testing showed that White patients were more likely to harbor anti-centromere antibodies (ACA) (26.6% vs. 9%, P<0.001) whereas Black patients were more likely to have anti-U1RNP antibody (24.6% vs. 6.2%, P<0.0001).

In this population recruited in a disease referral center, Black patients had more severe skin and lung involvements with lower prevalence of ACA as compared to White patients, supporting a more severe phenotype.