Background/Purpose: Acro-osteolysis (AO) is the bony resorption on the distal tufts of the digits, a characteristic radiological finding in Systemic Sclerosis (SSc) with estimated prevalence of 20-25% [1][2]. Some studies have suggested an association of digital ischemia and SSc specific auto-antibodies with AO [1][3][4], but the pathogenesis of AO remains poorly understood. Our goal is to better understand the factors associated with development of AO in SSc.

Methods:  We evaluated 168 outpatients who met criteria for SSc [5] and were seen between 2010 and 2015. We collected relevant clinical information, including laboratory and hand x-ray assessments, obtained within 5 years of this analysis. Patients were grouped by presence or absence of AO based on hand x-rays. Associations between potential risk factors and AO were assessed with unconditional logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for presence of AO.

Results: Of the 168 SSc patients studied, a total of 43 (26%) had AO. In univariate analysis, anti-topoisomerase I antibody (anti-topo I) and digital tip ulcers (DTUs) had the strongest association with AO (Table-1). In multivariate model, after adjusting for Anti-Topo I and DTUs (prior and current DTUs), AO was positively associated with Anti-Topo I (OR=4.3, 95% CI: 1.8-9.9), prior DTUs (OR=5.6, 95% CI: 2.2-14.2), current DTUs (OR=4.2, 95% CI: 1.9-9.4), and hand contractures (OR=3.3, 95% CI: 1.4-7.8), whereas AO was inversely associated with age of disease onset (OR=0.97, 95% CI: 0.94-0.99). Although not statistically significant, the Anti-centromere antibody was also inversely associated with AO (OR=0.4, 95% CI: 0.14-1.08). We found no associations of AO with current skin score, synovitis, tendon friction rubs, or RNA polymerase III antibody.

Conclusion: Our findings suggest that both digital ischemia and anti-topo I are strongly and independently associated with AO. Additionally, AO was strongly associated with hand contractures and younger age of disease onset. Prospective studies are needed to confirm if more aggressive treatment of digital ischemia in this subset of patients will lead to lower risk of AO and hand contractures.    References:

1-     Avouac et al. Ann Rheum Dis. 2006; 65:1088

2-     Arslan Tas et al. Rheumatol Int. 2012; 32:3581

3-     Johnstone et al. Rheumatol. 2012; 51:2234

4-     Steen et al. Semin Arthritis Rheum. 2005; 35:35

5-     Hoogen et al. Ann Rheum Dis. 2013; 72:1747 & Arthritis Rheum. 2013; 65:2737          

*Documented by hand x-rays   **Documented on physical exam   ***Documented by high resolution CT scan of the chest                                                                        SSc: systemic sclerosis; DTU: digital tip ulcer; RA: rheumatoid arthritis; TFRs: tendon friction rubs; Anti-topo I: anti-topoisomerase I or Scl70; RNA pol III: anti-RNA polymerase III antibody; ACA: anti-centromere antibody; OA: osteoarthritis; ILD: interstitial lung disease; mRSS: modified Rodnan skin score