Early diffuse cutaneous systemic sclerosis (dcSSc) has the highest case fatality among rheumatic diseases. We report baseline characteristics, current immunosuppressive therapies, progression of skin and internal organ involvement, and mortality in a multicenter prospective cohort from the United States (US) of America.We performed a longitudinal analysis of participants from 12 US centers, from April 2012 to July 2020. All participants had early dcSSc or were at-risk for dcSSc, with ≤2 years since the first non-Raynaud's phenomenon (RP) symptom.Three hundred one patients were included with a baseline median disease duration of 1.2 years since RP and a mean modified skin score of 21.1 units. At baseline, 263 (87.3%) had definite dcSSc and 38 (12.7%) were classified as at-risk; 112 (49.6%) patients were positive for anti-RNA polymerase III antibodies. The median follow-up duration was 24.5 months (IQR = 10.3-40.7 months). One hundred ninety (63.1%) participants were treated with an immunosuppressive therapy, of which mycophenolate mofetil was most used at baseline and follow-up. Of 38 who were classified as at-risk at baseline, 27 (71%) went on to develop dcSSc; these patients were characterized by higher baseline mean HAQ-DI (0.8 versus 0.4, p = 0.05) and higher baseline mRSS (8.8 versus 4.4, p < 0.01) in comparison with those who remained as limited cutaneous SSc. In the overall cohort, 48 participants (21.1%) had clinically significant worsening of skin fibrosis, mainly occurring in the first year of follow-up; 41 (23.3%) had an absolute forced vital capacity decline of ≥10%. Twenty participants (6.6%) died, of which 18 died in the first 3 years of follow-up. Cardiac involvement (33.3%), gastrointestinal dysmotility (22.2%), and progressive interstitial lung disease (ILD) (16.7%) were the main causes of death.This US cohort highlights the management of early SSc in the current era, demonstrating progression of skin and lung involvement despite immunosuppressive therapy and high mortality due to cardiac involvement.

Clinical characteristics, visceral involvement, and mortality in at-risk or early diffuse systemic sclerosis: a longitudinal analysis of an observational prospective multicenter US cohort