Solar Lentigines: Multiple Brown Macules Associated with Age
Multiple brown macules associated with age are called solar lentigines, also known as age spots or lentigo senilis.
Characteristics of Solar Lentigines
Solar lentigines are benign, hyperpigmented macules that develop in chronically sun-exposed areas of the skin, most commonly appearing after age 30-50 as a sign of photoaging 1, 2. They present with the following features:
- Light brown to black pigmented lesions of various sizes
- Typically appear on sun-exposed areas such as the face and back of hands
- Increase in prevalence with advancing age
- Associated with chronic UV exposure and photodamage
Histopathology
Solar lentigines have distinctive histological features that differentiate them from other pigmented lesions:
- Elongated rete ridges with increased melanin at the tips
- Normal number of melanocytes (not increased)
- Increased melanin pigment from the basal layer up to the stratum corneum
- Exaggerated formation of rete ridges in lesional epidermis 3
Clinical Significance
While solar lentigines are generally benign, they have important clinical implications:
- They represent a marker of cumulative sun damage
- May be associated with an increased risk for skin cancer 2
- Multiple solar lentigines of the upper back and shoulders (MSLBS) have been associated with past severe sunburns and melanoma risk 4
Differential Diagnosis
It's important to distinguish solar lentigines from other pigmented lesions:
- Freckles (ephelides): Smaller, lighter, and fade in winter; increase in melanin but not melanocyte number
- Lentigo maligna: Precursor to lentigo maligna melanoma, with irregular borders and color variation
- Seborrheic keratosis: Waxy, "stuck-on" appearance with rough surface
- Lentigines in RASopathies: Such as in NS with multiple lentigines (NSML, formerly LEOPARD syndrome), which appear around ages 4-5 years as hypertrophic, black-brown macules predominantly on the face 5
Management
Management options for solar lentigines include:
- Prevention: Sun protection is crucial to prevent development of new lesions
- Topical treatments: Retinoids, hydroquinone, azelaic acid
- Procedural treatments:
- Cryotherapy
- Laser therapy (Q-switched ruby laser has shown success) 1
- Chemical peels
Clinical Monitoring
Regular skin examinations are recommended for patients with multiple solar lentigines, especially if they have:
- History of severe sunburns
- Multiple lesions on the upper back and shoulders
- Other risk factors for skin cancer
Conclusion
Solar lentigines are common benign pigmented lesions that represent a cosmetic concern for many patients but may also serve as markers of photodamage and potentially increased skin cancer risk. Regular monitoring and sun protection are essential components of management.