Solar Lentigo

1. Epidemiology
   1. Onset over age 30-40 years
   2. Most common in Caucasian skin (also seen in asians)
2. Pathophysiology
   1. Proliferation of basal Melanocytes, increasing melanization in response to Sun Exposure
   2. Contrast with Freckles which are a result of increased Melanin production
3. Signs
   1. Characteristics
      1. Small Macules 1-3 cm (up to 5 cm), well circumscribed
      2. Light yellow to light brown to dark brown in color (may be variegated)
      3. Round or oval with slightly irregular border
   2. Distribution: Chronically sun exposed areas
      1. Forehead
      2. Cheeks
      3. Nose
      4. Hand and Forearm dorsum
      5. Upper back
      6. Chest
      7. Shins
4. Differential Diagnosis
   1. Hyperkeratotic lesions (distinguish from the smooth flat surface of Lentigo)
      1. Flat Seborrheic Keratosis
      2. Pigmented Actinic Keratosis
   2. Lentigo maligna (biopsy if suspected)
   3. Ephelides (Freckles)
   4. Cafe Au LaitMacules
   5. Syndrome with multiple Lentigines
      1. Peutz-Jeghers Syndrome
      2. LEOPARD Syndrome
      3. LAMB Syndrome
5. Red Flags (suggesting biopsy)
   1. Rapid growth
   2. Lesions suspicious for Melanoma
   3. Symptomatic lesions
      1. Pain
      2. Recurrent bleeding
      3. Poor healing
6. Management
   1. Light Cryotherapy (<5 seconds) with Liquid Nitrogen
      1. Risk of Hyperpigmentation
      2. Lesion will disappear for 1 to 3 years
   2. Combination Therapy (effective)
      1. Tri-luma (Hydroquinone 2%, Tretinoin 0.05%, Flucinolone 0.01%)
      2. Consider combining with light Cryotherapy
   3. Chemical Peel (recurrence is common)
      1. Trichloroacetic acid (Trichlor) 30-35%
   4. Laser therapy (ND:YAG Laser)
      1. Risk of Postinflammatory Hyperpigmentation
   5. Bleaching with Hydroquinone (Eldoquin Forte) 3-4%
      1. May result in blotchy Hyperpigmentation (ochronosis) and may take months to see result
      2. Also risk of acne-type eruption and Hypersensitivity Reaction
   6. Mequinol 2%/Tretinoin 0.01% (Solage) topical solution
   7. Keratolytics (less evidence than with other methods)
      1. Tretinoin (Retin A) 0.025 to 0.05%
      2. Tazarotene (Tazorac) 0.1% cream
      3. Adapalene (Differin) 0.1-0.3% gel
7. Prevention
   1. Regular use of Sunscreen (esp. fair skin types 1-3)
   2. Avoid Sunburns before the age of 20 years old
8. References
   1. Plensdorf (2017) Am Fam Physician 96(12): 797-804 [PubMed]
   2. Plensdorf (2009) Am Fam Physician 79(2): 109-16 [PubMed]