Background/Purpose: Skin involvement may be evaluated in systemic sclerosis (SSc) by modified Rodnan skin score (mRSS), the validated method to distinguish between patients with limited (lcSSc) or diffuse (dcSSc) cutaneous skin involvement (1). In lcSSc the skin involvement is confined to the extremities (hands, forearms, feet, legs and face), whilst it is present also on arms, chest, abdomen and thighs in dcSSc patients (2). However, mRSS is unable to identify slight alterations in dermal thickness (DT) (3), and several studies report the utility of high frequency skin ultrasound (US) for early identification of skin involvement in SSc patients (4,5). DT was found progressively higher in SSc patients with worsening pattern of nailfold microangiopathy (5).

The aim of this study was to measure DT by US in both SSc patients and healthy subjects, looking for differences between the groups and correlations between US and mRSS.

Methods: Forty-eight SSc patients (ACR/EULAR criteria) (mean age 64±11SD years, mean disease duration 6±5 years) and 20 healthy subjects (mean age 66±14 years) were enrolled, after informed consent (1). Dermal thickness (DT) was evaluated by both mRSS and US transducer with 22 MHz frequency (Esaote, Genoa, Italy) at the level of the usual seventeen skin areas (cheeks, fingers, dorsum of hands, forearms, arms, chest, abdomen, thighs, legs, feet) in both SSc patients and healthy subjects. Nailfold videocapillaroscopy (NVC) was also performed to detect and classify SSc patients into the proper pattern of nailfold microangiopathy (“early”, “active” or “late”) (6).

Results: By US, DT was found significantly higher in both dcSSc and lcSSc patients than in healthy subjects in all the seventeen skin areas (median total DT 21.5 vs 19.1 vs 14.9 millimetres, respectively; p<0.01). Of great importance, lcSSc patients showed a statistically significant higher DT than healthy subjects in all the skin areas even with normal mRSS (mRSS=0), in contrast with the classificative diagnosis of lcSSc (median DT 1.20 vs 0.86 for right arm, 1.10 vs 0.86 for left arm, 1.30 vs 1.13 for chest, 1.40 vs 1.13 for abdomen, 1.40 vs 1.10 for right thigh, 1.40 vs 1.10 for left  thigh, respectively; p<0.01). A significant progressive increase of DT was observed by US in SSc patients with different NVC pattern of microangiopathy at the level of all areas  (median total DT 17.53 vs 21.20 vs 21.43 millimetres respectively for “early”, “active”, or “late” pattern, p<0.05). Finally, a statistically significant positive correlation was found between mRss and US in DT evaluation (r=0.67, p<0.0001).

Conclusion: This study demonstrates the utility of high frequency skin US to detect the subclinical diffuse dermal involvement even where the mRSS is normal in patients with lcSSc. This observation could make a contribution for future classification of the disease.

References: 1. Clements PJ, et al. Arthritis & Rheumatism 2000; 43: 2445–54. 2. LeRoy EC, et al. J Rheumatol 2001;28:1573–6.   3. Hachulla E, et al. Clinic Rev Allerg Immunol 2011; 40: 78-83.  4. Moore TL, et al. Rheumatology 2003; 42: 1559-63.   5. Sulli A, et al. Ann Rheum Dis. 2014; 73: 247-51.  6. Cutolo M, et al. Nature Rev Rheumatol. 2010;6:578-87.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/identification-of-subclinical-skin-involvement-by-high-frequency-ultrasound-in-systemic-sclerosis-patients/