Background Although modified Rodnan skin score (mRSS) is the most widely used measure for assessment of skin involvement in Systemic Sclerosis (SSc), ultrasound (US) of skin thickness seems to be a promising complementary tool. (1)

Objectives To compare skin thickness measured by US of a defined anatomical point between SSc patients and age and sex matched controls. To compare, among patients, US measurements of skin thickness with local and total mRSS and other specific clinical variables.

Methods Forty-eight SSc patients and 45 age and sex matched controls were evaluated in a cross-sectional study at our Rheumatology Unit. SSc patients had a mean age of 56.98±12.73 years and mean disease duration of 9.77±6.12 years; 42 patients had limited cutaneous disease. Regarding US assessment, skin thickness was arbitrarily defined as thickness of epidermis, dermis and subcutaneous tissue, in millimetres, measured at the 2nd finger of both hands of each subject on the dorsal aspect of the proximal phalange. Examination was performed with a 15 MHz linear probe of a General Electric LOGIQ S8 US. For comparison between groups, mean skin thickness (mST) of combined right and left side was used. Patients' local and total mRSS were also assessed. Hand mobility in SSc (HAMIS) was calculated to evaluate functional disability and SSc Severity Scale (SScSS) to estimate activity and damage. Additional data was also collected from patients' clinical charts. Statistical analysis included Mann-Whitney U-test, Kruskal-Wallis and Spearman correlation coefficient test. Statistical significance was defined as P value <0.05.

Results SSc patients showed higher mST (3.17 mm [2.56 to 3.58]) (median [interquartile range]) compared with controls (1.89 mm [1.55 to 2.08]) (p<0.001). Among SSc group, skin thickness measured by US of both 2nd fingers of each patient strongly correlated with local mRSS assessed by palpation (Spearman's rho=0.698, p<0.001 and rho=0.645, p<0.001 for right and left sides, respectively). US mST was also correlated with total mRSS (rho=0.568, p<0.001), HAMIS (rho=0.520, p<0.001) and SScSS (rho=0.524, p<0.001). A higher mST was found in patients clinically classified with oedematous phase (p<0.001) and in diffuse cutaneous subtype (p=0.039). A mild association was observed for patients with digital ulcers (p=0.05). Age, gender, disease duration and the presence of calcinosis were not associated with US mST (p>0.05).

Conclusions US measurements of skin thickness of 2nd fingers were significantly higher in SSc patients compared with age and sex matched controls. US mST strongly correlated with local and total mRSS and was significantly higher in the presence of oedema, digital ulcers and in patients with diffuse subset. US mST also reflected functional disability and damage.

References

1. Hesselstrand R et al. High-frequency ultrasound of skin involvement in systemic sclerosis reflects oedema, extension and severity in early disease. Rheumatology (2008) 47 (1): 84–87.

References

Disclosure of Interest None declared