Atrophic and Hypertrophic Photoaging: Clinical, Histological, and Molecular Features of Two Distinct Phenotypes of Photoaged Skin

Abstract Background Exposure to the sun causes premature skin aging, known as photoaging. Clinical features of photoaging vary widely among individuals. In one form, skin appears thin with telangiectasia, while in another form, skin appears thickened with coarse wrinkles. Etiological, clinical, and therapeutic distinctions among different forms of photoaging remain largely unknown. Objective To characterize the clinical, histological and molecular features of hypertrophic and atrophic photoaging. Methods Fifty-three individuals were clinically classified as having primarily atrophic, or hypertrophic photoaging, or neither (controls). Subjects' demographic and sun exposure- related lifestyle data were captured by questionnaire. Fifteen clinical features of each subject were qualitatively or quantitively scored. Facial biopsies were analyzed for gene expression and histological characteristics. Results Actinic and seborrheic keratosis, telangiectasia, and prior incidence of skin cancers were statistically significantly greater, while photoaging scale severity, coarse wrinkles, thickness, and sallowness were significantly less, in atrophic versus hypertrophic groups. Histology also revealed significantly less elastotic material in atrophic photoaging. Gene expression of matrix metalloproteinases and collagens did not differ between the two forms of photoaging. Limitations The study was not designed to identify other possible subtypes of photoaging. Conclusion Systematic, categorical and quantitative clinical and histological assessments distinguish atrophic and hypertrophic photoaging.