Shear Wave Elastography for Non-Invasive Assessment of Skin Involvement in Systemic Sclerosis.

Background/Objectives: Systemic sclerosis (SSc) is an autoimmune fibrosing disorder in which cutaneous involvement is a major manifestation. We investigated whether shear wave elastography (SWE) can distinguish SSc from healthy controls and examined how SWE relates to clinical and histological indices of skin fibrosis. Methods: The study included 78 patients with SSc and 30 healthy controls (HCs). High-frequency ultrasound (HFUS) quantified skin thickness and SWE quantified stiffness at the fingers, dorsal hands, and forearms. Ultrasound findings were examined in relation to the modified Rodnan Skin Score (mRSS). In 15 patients with diffuse cutaneous SSc (dcSSc), matched forearm biopsies were additionally analyzed for dermal thickness and collagen content. Results: Relative to HCs, patients with dcSSc had greater epidermal and dermal thickness at all examined sites, while patients with lcSSc had greater dermal thickness only at the fingers. Associations between dermal thickness and mRSS varied by site (Spearman ρ, 0.47-0.66). SWE values were higher in SSc than in HCs. The AUCs for distinguishing SSc from HCs were 0.820 at the fingers, 0.734 at the dorsal hands, and 0.760 at the forearms. Within the dcSSc biopsy subgroup, SWE correlated with collagen volume fraction (ρ = 0.68, p = 0.0068) and histological dermal thickness (ρ = 0.63, p = 0.0142). Conclusions: SWE enables quantitative non-invasive characterization of skin stiffness in SSc. Matched forearm histology in a small dcSSc subgroup provides preliminary evidence that the imaging measurements converge with tissue-level measures. Validation in larger independent cohorts is needed.