The effect of topical tretinoin on photodamaged facial skin: the Thai experience.

Because of the climate in Bangkok, Thailand, a prematurely aged appearance is common in adults beyond 40 years of age. Sixty-one Thai people with moderate to severe signs of dermatoheliosis applied 0.05% tretinoin cream to the face once daily for 6-12 months. Four-mm punch biopsies were obtained from the cheeks before and after treatment. These were formalin-fixed and evaluated histochemically. A surprising degree of photodamage was noted histologically in these dark-skinned people. After 6 months of tretinoin, epidermal atypia and atrophy were largely corrected. There was a great diminution in the density of melanin granules within keratinocytes and corneocytes. Tretinoin did not significantly affect the dermal matrix after 6 months. However, after 12 months, a thin band of new collagen was deposited beneath the epidermis, accompanied by the formation of new vessels (angiogenesis). By global assessment, after 12 months most subjects experienced at least moderate improvement in appearance, especially with regard to hyperpigmented spots and fine wrinkles.