2.1.2.2 Clinical manifestations and histological f...
1.Clinical manifestations
Clinical classification of photoaging can be divided into two categories：atrophic photoaging and hypertrophic photoaging.The former shows signs with fewer wrinkles and dysplastic premalignant changes such as actinic keratosis.The latter displays features with thick wrinkles，leathery skin，lentigines，and bronzed appearance；a yellow cobblestone appearance of the skin may also be present.
2.Histological features(https://www.daowen.com)
The histological features of photoaging include elevated elastosis and collagen fragmentation beneath the dermal-epidermal junction.The epidermal thickness and the morphology of epidermal cells can be irregular.There is an increase in the amount of glycosaminoglycans and proteoglycans with increased numbers of hyperplastic fibroblasts.The number of inflammatory cells also increases，such as mast cells，eosinophils，and mononuclear cells.Melanogenesis is upregulated following ultraviolet insult.