Background/Purpose: Anti-fibrillarin (AFA) auto-antibodies are rarely found in Systemic Sclerosis (SSc). Beyond the ethnic association with a higher prevalence in patients of Black ethnicity, the phenotype of AFA+ patients is poorly known. Our study aims at reporting the features of AFA+ SSc patients and analyzing the differences among ethnic groups.

Methods: We retrospectively evaluated the clinical data of patients from the first and last available visits in 16 European rheumatology SSc referral centers.

Results: A total of 142 AFA+ patients meeting the 2013 ACR-EULAR SSc classification criteria were recruited. It is of note that patients of Black ethnicity were 31 (22.5%) compared to 107 (77.5%) of White Caucasian origin. The mean duration of follow-up was 107.5 ± 83.2 months. Demographic and phenotype details are reported in Table 1, but the following highlights can be made. The diffuse cutaneous subset was more common in patients of Black origin: 22 (71%) compared to 32 (40%) (p  = 0.002). Correspondingly, the baseline modified Rodnan Skin Score was 14.1 ± 10.4 for patients of Black origin versus 6.98 ± 8.03 for those of White origin (p < 0.002). Regarding major organ involvement, in the whole cohort, renal crisis was observed in 7 patients (5%), interstitial lung disease (ILD) in 28 (20%), heart involvement in 15 (10.5%), myositis in 19 (13.5%), arthritis in 28 (20%) and digital ulcers (DU) in 50 patients (36.2%). When differences related to ethnicity were considered, we observed that renal crisis was more common in patients of Black origin (13% versus 3%, p = 0.025). Similarly, ILD was more common although not significatively in Black ethnicity (29% versus 18% p=0.177) with forced vital capacity and diffusion lung CO significatively lower compared to White patients, indicating a more severe lung phenotype in Black patients (Table 1). Regarding cardiovascular aspects, Pulmonary Arterial Hypertension and cardiac involvement were similarly distributed among the two groups (6.4% and 28.6% in Black compared to 5.6% and 27.7% in White patients, respectively). DU were more frequent in Black (45%) compared to White individuals (35%). Regarding musculoskeletal involvement, myositis was present in 17% of Black patients compared to 10% of White (p = 0.077) showing a  trend towards significance. Arthritis prevalence was similar into two groups. With regards to longitudinal data, the overall mortality rate was 10.5%, with SSc-related deaths accounting for 6 (40%) cases without any difference among the 2 ethnic groups although the low number of events precludes careful analyses.

Conclusion: Our study provides a detailed description of AFA+ SSc patients a poorly known SSc subset. AFA+ individuals of Black origin have significantly more severe disease, particularly with skin and pulmonary involvement, and a higher prevalence of renal crisis. This comprehensive analysis underscores the severe profile overall in AFA+ SSc patients and also the importance of considering ethnic differences in the clinical management. We are collecting additional data from AFA+ SSc patients through collaboration with additional centers from outside Europe to enlarge the series and explore whether ethnic differences also apply.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/features-of-anti-fibrillarin-positive-systemic-sclerosis-patients-and-ethnic-differences-a-european-multicenter-cohort/