Late skin fibrosis in systemic sclerosis: a study from the EUSTAR cohort

The role of skin ultrasound in systemic sclerosis: looking below the surface to understand disease evolution

Skin ultrasound has shown promising results in the evaluation of skin involvement in patients with systemic sclerosis, as substantiated by a recent systematic literature review from the World Scleroderma Foundation Skin Ultrasound Working Group. In this Viewpoint, we will discuss the role of ultrasound in evaluating skin involvement in patients with systemic sclerosis, particularly the possibility of using this technique to detect an early subclinical skin involvement from the very early phase, suggesting its possible use in both diagnosis and disease follow-up. To detect subclinical skin involvement, it is essential to understand the difference between the skin of patients with systemic sclerosis and that of healthy controls, including defining exactly which structures are affected by the disease and which are spared. The potential of this non-invasive technique might suggest its future role in both clinical practice and clinical trials, possibly replacing invasive and painful procedures such as skin biopsies and promoting patient retention in clinical trials.

Scleroderma Skin: How Is Treatment Best Guided by Data and Implemented in Clinical Practice?

As skin involvement is the hall mark of systemic sclerosis (SSc) and changes of skin involvement have shown to correlate with internal organ involvement, assessing the extend of skin involvement is key. Although the modified Rodnan skin score is a validated tool used to evaluate the skin in SSc, it has its drawbacks. Novel imagine methods are promising but should be further evaluated. As for molecule markers for skin progression there are conflicting data on the predictive significance of baseline SSc skin gene expression profiles, but immune cell type signature in SSc skin correlates with progression.

Normal percentile reference curves for skin ultrasound thickness and stiffness at Rodnan sites

Objectives

Our primary objective was to establish preliminary normal reference curves for ultrasound–dermal thickness and skin stiffness in the 17 Rodnan skin sites, considering the effect of gender and age on these measures. As an exploratory objective, we investigated the effect of body mass index and the menopause on skin ultrasound measures.

Methods

A cross-sectional study was conducted involving 140 healthy volunteers, aged 20–79 years. Recruitment was stratified by gender and age (10-year categories). Ultrasound–dermal thickness and skin stiffness were assessed by high-frequency ultrasound and shear-wave elastography, respectively, at the 17 Rodnan skin sites. Outcomes were evaluated through a mixed linear model, univariate and multivariate regressions. Normal reference curves were derived for both ultrasound measures in each skin site. An online calculator of the percentiles of skin ultrasound measures was developed.

Results

Ultrasound–dermal thickness and stiffness measures were higher in men than women in all Rodnan skin sites (except in chest for ultrasound–dermal thickness). Age had also a significant impact in both ultrasound measures, but only in some skin sites. Gender and age percentile curves (97.5th, 95th, 75th, 50th, 25th, 5th, 2.5th) were plotted for each of the measures in each skin site.

Conclusions

Gender and age are strongly associated with skin ultrasound parameters, imposing the need for gender-specific and age-specific reference values. Normal reference percentile curves are provided as a basis for future cooperative work to strengthen its evidence basis, representativeness and refinement regarding potentially influential factors.