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INTRODUCTION

KEY POINTS

  • Solar lentigines are hyperpigmented macules that are round or oval in shape with slightly irregular edges.

  • They are common in skin of color populations except among South Asians with skin of color.

  • Ultraviolet light exposure and genetic predisposition are the most important factors in the development of solar lentigines.

  • Treatment may include physical modalities and depigmenting agents.

  • Sun avoidance, protective clothing, sunscreen, and blocking agents are indicated to prevent solar lentigines.

Solar lentigines (SLs) are benign, hyperpigmented macules that occur on sun-exposed areas of the skin.1,2,3,4 They are induced by natural or artificial sources of ultraviolet (UV) radiation and are also called sun-induced freckles, sunburn freckles, freckles in adulthood, age spots, actinic lentigines, and senile lentigines.5,6

EPIDEMIOLOGY, ETIOLOGY, PATHOGENESIS, AND HISTOPATHOLOGY

This benign pigmentary disorder is prevalent among fair-skinned patients with Fitzpatrick skin types I or II (those who always burn and who tan a little or not at all).5,7 The incidence increases with age, affecting more than 90% of those with Fitzpatrick skin type I to III older than 50 years.2,3,4,8 SLs are also a clinical features of photoaging in East and Southeast Asian populations. In this skin of color population, discrete pigmentary changes, including SLs and mottled hyperpigmentation, are seen frequently.9 In a study by Chung et al10 of Koreans aged 30 to 92 years, hyperpigmented macules were the major pigmentary lesions associated with photoaging in women. The number of hyperpigmented macules increased with each decade of age in Fitzpatrick skin types I to III.10

Bastiaens et al6 demonstrated that SLs have a positive association with cumulative lifetime sun exposure and early sun exposure [Figure 53-1]. There is also a possible genetic susceptibility to the development of SLs in response to acute or chronic UV exposure.5 Aoki et al11 demonstrated that SLs are induced by the mutagenic effect of repeated UV exposure in the past, leading to the characteristic enhancement of melanin production together with decreased proliferation and differentiation of lesional keratinocytes against a background of chronic inflammation.

FIGURE 53-1.

Solar lentigines on the chest of a patient who had early and intense sun exposure.

SLs may appear after chronic photochemotherapy (6 to 8 months). However, individual susceptibility factors such as race, age, and tanning and burning responses to sunlight are important to determine the prevalence and density of SLs.5 Recently, a study observed that, in addition to age and constitutive host factors, current intake of oral contraceptives or progestogen treatments may be associated with SLs.12

The histopathology of SLs shows a linear increase in melanocytes along the dermal-epidermal junction.13 There ...

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