The Role of Autoimmunity on the Relation Between Erosions and Bone Mineral Density in Rheumatoid Arthritis: A Clinical Research

Abstract IntroductionBoth erosions and osteoporosis are present in rheumatoid arthritis and are related to RANK-L pathway activation. The aim of the study was to evaluate the relationship between erosion and bone mineral density (BMD) in RA and whether it can be driven by autoimmunity.Patients and methodsPatients followed in the Department of Rheumatology between January 2008 and May 2019 satisfied the 1987 ACR or 2010 ACR-EULAR criteria. Erosions were evaluated by the modified Sharp/van der Heidje erosion score (SHSe) on radiographs and bone mineral density (BMD) in g/cm2 and by the T-score at the hip on DXA. The presence and titers of ACPA as well as rheumatoid factor (RF) and anti-nuclear antibodies (ANAs) were recorded at intervals of less than 2 years for both DXA and radiography.ResultsA total of 149 patients met the inclusion criteria. A total of 61.1% were ACPA positive, 79.9% were erosive and 10.7% had a hip T-score ≤-2.5. ACPA status but not titers was associated with a higher erosion score (63.0 (53.2) for ACPA + vs. 45.5 (44.1) for ACPA – (p= 0.04)). ACPA titers were associated with lower BMD at the hip (value -0.216; p=0.01) but not with T-score. A higher erosion score was associated with a lower BMD (R2: 0,049 and value: -0.222; p=0.009) and T-score (R2: 0,158 and value -0.397; p<0.0001) at the hip. In linear regression, erosion and systemic bone loss were still associated with but not driven by ACPA status or titer. RF and ANA did not demonstrate any role in this association.ConclusionWe showed that the relationship between erosion and bone mineral density associated with RA does not seem to be driven by ACPA or other autoimmunity parameters. However, the presence of ACPA or erosion should lead to osteoporosis assessment.