Background Skin manifestations are critical in the initial diagnosis of systemic sclerosis (SSc) and in the subsequent sub-classification into the different subsets of the disease (1). The modified Rodnan skin score (mRSS) is the validated method to detect both severity and extension of skin involvement, and high frequency ultrasound (US) is a valid and reproducible technique to measure dermal thickness (DT) in patients with SSc (2-4). Furthermore, US is able to detect early skin involvement in SSc patients (5-7).
Objectives To study by US possible subclinical skin involvement in limited cutaneous SSc (lcSSc) patients, in those skin areas apparently not affected on the basis of a normal mRSS.
Methods Fifty lcSSc patients (mean age 62±13SD years, mean disease duration 5±5SD years) and fifty healthy subjects (mean age 62±11SD years) were analysed during clinical follow-up and after informed consent (8). Both mRSS and US were used to evaluate DT in the usual seventeen areas of the skin (cheeks, fingers, dorsum of hands, forearms, arms, chest, abdomen, thighs, legs, feet) of SSc patients. Skin US was also performed in the same seventeen areas of healthy subjects, looking for DT differences in comparison with SSc patients. Statistical analysis was carried out by non parametric tests.
Results DT was found by US significantly higher in lcSSc patients than in healthy subjects in all skin areas with exclusion of thighs (median millimetres 0.86 vs 0.67 for cheeks, 0.85 vs 0.69 for right finger, 0.88 vs 0.68 for left finger, 0.78 vs 0.69 for dorsum of right hand, 0.81 vs 0.69 for dorsum of left hand, 0.99 vs 0.76 for right forearm, 0.98 vs 0.77 for left forearm, 1.00 vs 0.83 for right arm, 1.05 vs 0.83 for left arm, 1.30 vs 1.11 for chest, 1.30 vs 1.12 for abdomen, 0.99 vs 0.93 for right leg, 0.98 vs 0.93 for left leg, 0.94 vs 0.87 for right foot, 0.95 vs 0.89 for left foot, respectively, p<0.0001 for all. At the level of the thighs DT was higher in lcSSc patients than in healthy subjects, but this was not statistical significant (median millimetres 1.20 vs 1.10 for both right and left thigh, p=0.16 and p=0.24 respectively). Of interest, as above reported, DT was significantly higher in lcSSc patients than in healthy subjects in four out of six skin areas where the mRSS was normal (=0) in agreement with the diagnosis of lcSSc (arms, chest, and abdomen).
Conclusions This study strongly suggests that subclinical diffuse dermal involvement may be detectable by high frequency ultrasound already in patients with limited cutaneous SSc. This observation is of great relevance for future classification of SSc subsets of disease, and it seems linked to the observation that patients with both lcSSc or diffuse cutaneous SSc may display similar organ/laboratory involvement in clinical studies.
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Disclosure of Interest None declared