Author: Bob Chan, Dermatology Registrar, Auckland Hospital, Auckland, New Zealand, 2014.
Solar lentigo is a harmless patch of darkened skin. It results from exposure to ultraviolet (UV) radiation, which causes local proliferation of melanocytes and accumulation of melanin within the skin cells (keratinocytes). Solar lentigos or lentigines are very common, especially in people over the age of 40 years. Sometimes they are also known as an “old age spot” or “senile freckle”.
A solar lentigo is a flat, well-circumscribed patch. It can be round, oval or irregular in shape. Colour varies from skin-coloured, tan to dark brown or black, and size varies from a few millimetres to several centimetres in diameter. They can be slightly scaly.
Solar lentigines are found as groups of similar lesions on sun-exposed sites, particularly the face or the back of hands. They occur in light and dark skin, but tend to be more numerous in fair-skinned individuals.
Solar lentigo is often diagnosed on its clinical appearance. On occasion, it can be difficult to differentiate an irregular solar lentigo from melanoma, a potentially dangerous form of skin cancer, and the term atypical solar lentigo may be used.
Seborrhoeic keratoses may arise within solar lentigines. This results in localised thickening and change in texture within the lentigo.
Solar lentigines may become inflamed, when they are called lichenoid keratoses or lichen-planus like keratoses (due to the pattern of inflammation seen on histopathology). Lichenoid keratoses gradually disappear.
Bleaching agents such as hydroquinone are not effective.
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