Skin involvement in systemic sclerosis.

Skin thickening is a characteristic feature of SSc. More extensive skin involvement coincides with more severe internal organ manifestation(s), poor prognosis and increased disability, at least in the early phase of the diffuse cutaneous scleroderma subset. The fully validated, feasible method ('gold standard') for measuring the dermal skin thickness is the modified Rodnan skin score (mRSS). The responsiveness of mRSS was somewhat modest in clinical trials, and a careful teaching process is necessary. Parallel method(s) for measuring skin thickness need to be used in the future. Ultrasound (US) measurement of the dermis with a 20-30 MHz probe is a valid, reproducible and responsive method in patients with dcSSc. However, US is time-consuming and requires a training process. Of the mechanical instruments available, only the durometer, which measures the hardness of skin, has been validated. The inter- and intra-observer reproducibility and sensitivity to change of durometry were good, and correlated with mRSS and US-measured skin thickness. Several further mechanical instruments exist including the elastometer, twistometer, cutometer and plicometer. They seem to distinguish between involved and non-involved skin, and therefore merit further evaluation. The measurement of late-stage, irreversible skin damage/atrophy should be resolved in the future through the development and validation of new instruments.