Background Osteoporosis (OP) is considered a common features in patients with inflammatory rheumatic disease[1]. Psoriatic arthritis (PsA) is a chronic inflammatory arthritis of unknown aetiology and joint bone erosions are frequent, but the relationship between their presence and systemic OP has been rarely investigated.

Objectives The aim of this cross-sectional study is to analyze bone mineral density (BMD), T and Z scores in PsA patients as well as to investigate its possible association with the presence of joint bone erosions.

Methods A total of 65 patients (mean age 61.4±11.8 years) affected by PsA and 30 age-matched healthy controls (mean age 64.0±6.5 years) were studied. The presence or absence of joint bone erosions was evaluated by hands and feet x-ray. BMD of lumbar spine (L₁-L₄) and the proximal femur (total hip) was analyzed using dual-energy X-ray absorptiometry (DXA) scan (Lunar Prodigy, GE, USA). The results of BMD were expressed in g/cm² and according to the WHO definition, osteoporosis was diagnosed at T score less -2.5 and osteopenia at T-score between -1.0 and -2.5 at any site. The statistical analysis was performed on 2 separate group: group A (32 patients with bone erosions) and group B (33 patients without bone erosions).

Results Out of 65 patients enrolled 27 (41.5%) presented generalized bone loss, in particular 21 (32.3%) showed osteopenia and 6 (9.2%) osteoporosis. BMD was found significantly lower in the PsA patients than controls at lumbar spine and total hip (lumbar spine: 1.114±0.19 g/cm² vs 1.229±0.08 g/cm², p<0.000; total hip: 0.927±0.17 g/cm² vs 1.033±0.17 g/cm², p<0.05). Accordingly, T and Z-scores showed lower values in PsA compared to controls at lumbar spine and total hip (lumbar spine: T score -0.860±1.66 vs 0.145±0.64, p<0.0001; Z score: -1.707±3.70 vs 0.358±0.68, p<0.0001. Total hip: T score -1.186±1.25 vs 0.284±0.96, p=0,008; Z score: -0.586±1.15 vs 0.293±0.89, p=0.01). Group A was affected by osteopenia and osteoporosis in 59.4% and 12.5%, respectively. There was no difference in sex distribution in patients with osteopenia while 75% of subject with osteoporosis were female. In group B, 36.4% of patients showed osteopenia and 6% osteoporosis; all patients with osteoporosis were female. BMD, T and Z scores measured at lumbar spine were significantly lower in group A compared with group B (BMD: 1.048±0.12 g/cm² vs 1.185±0.2 g/cm², p =0.003; T score: -1.263±0.9 vs -0.094±1.74, p=0.003; Z score -1.519±3.46 vs 1.697±4.45, p=0.001). The comparison between the two groups showed no significance differences in total hip mineral density, T and Z scores.

Conclusions PsA patients appear be at significantly higher risk of osteoporosis than controls and patients with joint erosions show significantly increased bone loss at any level of the skeleton. The high bone turnover, due to the action of the inflammatory cytokines might partially explain the reason for the observed differences.

References

1. Bultink IE, Vis M. Inflammatory Rheumatic Disorders and bone. Curr Rheumatol Rep. 2012;14(3):224-30. Review

Disclosure of Interest None Declared