Solar lentigo (a type of lentigo also known as a senile lentigo, age spot, or liver spot) is a benign pigmented macule appearing on individuals with light skin that is related to ultraviolet radiation (UVR) exposure, typically from the sun. It must be distinguished from lentigo maligna.
Solar lentigines are believed to be UVR-induced proliferative responses of the epidermal keratinocytes and/or melanocytes, although the exact mechanism of formation is not completely understood. Ultraviolet B (UVB) exposure is thought to increase expression of keratinocyte growth factor, which thereby induces tyrosinase expression and melanin production in melanocytes. This melanin pigment is then transferred to keratinocytes where there is abnormal pigment retention.
Solar lentigines are more common in those with skin phototypes I-III and a history of multiple sunburns. They are present in 90% of individuals over 60 years of age who are of Northern European descent. They may also be seen in younger individuals with extensive UVR exposure and have been observed as early as 5 years of age in children with xeroderma pigmentosum. They are typically located on sun-exposed skin, including the face, upper chest, shoulders, dorsal arms, and hands. Solar lentigines are asymptomatic although they may enlarge, darken, or remain unchanged over time.
A variant is the psoralen ultraviolet A (PUVA)-induced lentigo, which is seen in approximately 50% of patients with at least 6 years of PUVA therapy and may sometimes be distinguished by large, somewhat atypical melanocytes on histopathology. These may be present on any body surface exposed to PUVA, including the genitalia.
ICD10CM: L81.4 – Other melanin hyperpigmentation
SNOMEDCT: 72100002 – Solar lentigo
Differential Diagnosis & Pitfalls
Lentigo simplex – Clinical appearance similar to solar lentigo, but lesions appear earlier in life and are not limited to sun-exposed skin.
Macular seborrheic keratosis – May be difficult to distinguish from a lentigo; however, lentigines are always macular with intact surface skin lines.
A solar lentigo (plural, solar lentigines), also known as a sun-induced freckle or senile lentigo, is a dark (hyperpigmented) lesion caused by natural or artificial ultraviolet (UV) light. Solar lentigines may be single or multiple. This type of lentigo is different from a simple lentigo (lentigo simplex) because it is caused by exposure to UV light. Solar lentigines are benign, but they do indicate excessive sun exposure, a risk factor for the development of skin cancer.
Who’s At Risk
Solar lentigines most commonly occur in older adults, particularly those who sunburn easily and fail to tan, but they may also occur in children.
Signs & Symptoms
Solar lentigines typically appear on areas exposed to natural or artificial UV light. They appear as well-defined, light brown to black, flat spots. In people who have been treated with a form of UV light therapy called PUVA, solar lentigines may occur in areas of the skin not exposed to UV light.
To prevent solar lentigines, avoid exposure to sunlight in midday (10 AM to 3 PM), wear sun-protective clothing (tightly woven clothes and hats), and apply sunscreen (SPF 30 UVA and UVB block).
When to Seek Medical Care
Solar lentigines do not require medical therapy, but see a physician for evaluation if they become cosmetically bothersome or if you are uncertain about any pigmented spot on your body.
If solar lentigines are cosmetically bothersome, your physician may:
Freeze the area lightly with liquid nitrogen.
Prescribe a bleaching cream (hydroquinone), but this is often not successful.
Bolognia, Jean L., ed. Dermatology, pp.983, 1760-1761. New York: Mosby, 2003.