| Abstract: | Background/aims: One clinical sign of photodamage is a sallow discolouration of the skin, and solar elastotic degenerative change in the upper dermis may cause this change. We have attempted to quantify these phenomena and relate them to each other and to age. Methods: Twenty-seven healthy volunteers (age 18 to 61 years) were recruited. We examined the back of the hand of photodamaged individuals and the inner upper arm to demonstrate changes due to ageing. Each site was assessed for cutaneous blood flux using a laser Doppler fluxmeter (PF4000, Perimed UK), and for melanin pigmentation using a Melanin Index meter (Dermotronics Ltd, Cardiff, UK). Skin colour was measured using a diode array spectrophotometer (MCPD-1000, Photal, Japan), which computes CIE coordinates L*, a*, b*. Biopsies from each site were obtained from 13 of the subjects and were processed and stained with Gomori's aldehyde fuchsin. The percentage area of elastic staining material in the dermis was measured using image analysis. Sections were measured in four bands of 200 micron depth, and four fields were measured per band. Results: Neither melanin content nor skin blood flux correlated with age for either skin site. Percentage area of elastosis correlated with age on the exposed site from the uppermost 600 microns of the dermis, (<200 micron depth, r=0.74, P<0.01, 200<depth<400, r=0.57, P<0.05; 400<depth<600, r=0.57, P<0.05). No correlation was found on the unexposed inner upper arm site. On the back of hand site, a linear relationship was found between a parameter derived from the L*, a*, b* coordinates of (b*-5a*) and both age (r=0.904, P<0.001) and percentage area of elastosis of the uppermost 200 microns of dermis (r=0.74, P<0.01). This was not seen for the inner upper arm site. On exposed sites, the coefficient (b*-5a*) correlates with solar elastosis and these both correlate with age, which is related to exposure. Conclusion: This data confirms that solar elastosis accounts for the yellowish discolouration of sun damaged skin, and suggests that the coefficient b*-5a* could be used for the non-invasive quantification of solar elastosis. |
