Skin elasticity in psoriasis. In vivo measurement of tensile distensibility, hysteresis and resilient distension with a new method. Comparison with skin thickness as measured with high-frequency ultrasound.

Abstract

ABSTRACTThe skin elasticity of psoriasis plaques was measured in 10 patients suffering from psoriasis vulgaris with a recently introduced in vivo method with high reproducibility. The method is based on repeated applications of suction to a 0.79cm2 circular skin area, and measurement of tensile distensibility (TD), hysteresis (H) and resilient distension (RD) by the principle of electrical capacitance as calibrated with distance. Measurements of 23 plaques showed a decrease in TD and increases in H and RD when compared to regional control measurements. Experiments in 19 control regions with histamine skin‐pricks to evaluate the effects of cutaneous oedema on skin rheology showed that TD as well as H and RD became increased. The skin thickness of the plaques was increased by 68% as a mean, probably resulting from oedema of the outer dermis. The decreased TD, representing a component of stiffness, is probably related to a fixed zone of interdigitation between elongated and club‐shaped rete ridges and oedematous papillae while the increase in H and RD, representing a component of softness, is probably explained by the oedema of the outer dermis. Analyses of the relation between increase in thickness and rheology indicated that, in more advanced plaques, the skin may be in a state of mechanical locking with low hysteresis.