medwireNews: Two studies published in Arthritis Research & Therapy describe the impact of psoriatic arthritis (PsA) and nonradiographic axial spondyloarthritis (axSpA) on bone structure.
In the first study, Georg Schett (Universitätsklinikum Erlangen, Germany) and colleagues demonstrated a significantly higher average number of bone erosions in the dominant hand as measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) among 101 PsA patients compared with 55 patients with psoriasis and 47 healthy controls.
And there was “a continuous increase in erosive bone changes with age” in all three groups, with PsA patients the most affected by bone erosion across all age groups, say the researchers. Indeed, among participants aged 20–40 years, those with PsA had 1.05 erosions per person, on average, compared with 0.27 for psoriasis patients, and 0.12 for healthy controls. The corresponding values were 1.26, 0.50, and 0.33 for those aged 41–60 years, and 2.00, 0.86, and 1.29 for participants older than 60 years.
“Hence, the amount of erosive bone changes in a 20 to 40-year old patient with PsA was as high as in healthy individuals aged over 60 years,” summarize Schett and team.
Moreover, patients with PsA had a significantly greater average number of enthesiophytes – bony spurs formed as a result of enthesial inflammation – in the dominant hand than individuals with psoriasis or healthy controls.
PsA patients had a “moderately increased” average number of enthesiophytes with age, at 7.50, 9.09, and 11.96 in the youngest, middle, and oldest age categories, respectively. However, age was not associated with the burden of enthesiophytes in patients with psoriasis or healthy controls.
The researchers also identified a significant association between disease duration and the burden of both bone erosions and enthesiophytes. In a regression model including variables such as age, sex, extent of skin disease, and BMI, only duration of skin disease was significantly associated with erosive bone changes and the number and size of enthesiophytes.
Together, the study results show that PsA is “associated with significant bone destructive changes, most likely because of late recognition of the disease and consequently late start of anti-inflammatory treatment,” conclude the investigators.
The second study, also by Schett and team, investigated bone changes occurring in nonradiographic axSpA. HR-pQCT analysis of the dominant hand demonstrated that 101 axSpA patients had a significantly lower median cortical area and thickness than 50 healthy controls, at 60 versus 65 mm2 and 767 versus 840 µm, respectively.
Median cortical volumetric bone mineral density (BMD) was also significantly lower in the axSpA versus control group (823 vs 846 HA/cm3), but trabecular BMD was comparable between the two groups.
Similar to the PsA findings, the study authors observed an association between axSpA disease duration and decreasing cortical BMD. The 55 patients with a disease duration of 2 years or longer had significantly lower BMD than the healthy controls, but the 46 patients with early disease (duration of less than 2 years) did not. However, Schett et al stress that cortical thickness was significantly decreased among early axSpA patients compared with controls (median 775 vs 840 µm), as well as among those with longer disease duration.
Therefore, “[b]one microstructure in patients with [nonradiographic]-axSpA is characterized primarily by deterioration of cortical bone,” which “starts early and is evident within the first 2 years of the disease,” write the researchers.
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