Skin elasticity in localized scleroderma (morphoea). Introduction of a biaxial in vivo method for measurement of tensile distensibility, hysteresis, and resilient distension of diseased and normal skin.

Abstract

ABSTRACTA method for measuring skin elasticity in vivo based on repeated applications of suction to a circular skin area with a diameter of 10 mm and measurement of tensile distensibility (TD), hysteresis (H), and resilient distension (RD) by the principle of electrical capacitance calibrated to elevation of the skin surface in mm is introduced. Measurements in 14 patients of 51 lesions of localized scleroderma (morphoea) and regional controls revealed a characteristic rheological pattern in the sclerotic state representing structural alterations with reduced TD and H; H became temporarily increased during remission. Measurements in control regions showed significant correlations between TD and H (r=0.382), and between H and RD (r=0.420). Regional differences between extremities, abdomen, and back were significant and “inversely” correlated to skin thickness as measured by ultrasound (r=0.451). The method was highly reproducible according to studies on silicone rubber membrane (SD of TD different sites, 0.023 mm; SD of H, 0.010 mm; SD of TD same sites repeated, 0.010 mm). The biological, day‐to‐day variation in different regions of a healthy individual was considerably higher (SD of TD, 0.048–0.087 mm), in particular with respect to H (SD, 0.122–0.277 mm). TD was very variable. Experiments on abdominal skin showed that previous mechanical stress resulted in a characteristic pattern with an increase in TD and a decrease in H. Acute edema (histamine weal) resulted in a characteristic pattern with increased TD and H. Both experiments illustrated functional aspects of skin rheology overlying the structure and explaining part of the biological variation.