What are Lentigines?
A lentigo (plural: lentigines) is an area of the skin that is flat or slightly raised and pigmented, usually tan, brown, or black. Lentigines are mostly seen in areas of the body that are exposed to the sun frequently. They are irregular in shape and vary in size.
They are more commonly seen in the middle age and older population, and the number of spots tends to increase with age. They appear suddenly or grow in size over the years.
Lighter-skinned people have a higher chance of getting these sunspots. Increased exposure to the sun, multiple sunburns, phototherapy, and radiation therapy can increase your risk for lentigines.
Types of Lentigines
Based on where the lentigines appear on your body and their cause, the different types of lentigos are
1. Lentigo simplex - the most common type found on your arms, legs, and trunk. They are often seen from childhood and can fade away with time.
2. Solar lentigo - mostly seen in people older than 40 years. The UV radiation in the sun rays causes this pigmentation to occur as spots on sun-exposed areas. These are also called age spots.
3. Inkspot lentigo - seen in lighter-skinned people who have sunburns
4. PUVA lentigo - seen after PUVA (psoralen and ultraviolet A radiation) therapy used to treat psoriasis and eczema
5. Radiation lentigo - seen in places exposed to radiation therapy, usually in cancer treatment
Symptoms of Lentigines
Sunspots are not itchy and do not have any other symptoms. They just appear on your skin on exposure to UV radiation. They are usually not a cause for medical concern unless they are triggered by an underlying syndrome.
Inherited Conditions Associated with Lentigines
Certain inherited syndromes are associated with lentigines and can increase your risk of getting them. These include:
Cowden syndrome
Noonan syndrome
Peutz-Jeghers syndrome
Xeroderma pigmentosum
Bannayan-Riley-Ruvalcaba syndrome
Evolutionary Relevance of Lentigines
The geographical location is the link between evolution and lentigines. There appears to be an evolutionary purpose of freckles in humans. People who lived in places with higher sun exposure had a darker skin color. This is due to the excess production of melanin, which protects the skin from the harmful effects of ultraviolet radiation (UVR). Lighter-skinned people often have ancestry that evolved with less exposure to sunlight. When these people are exposed to more sunlight than usual, pigmentations like sunspots occur.
How Genes Influence the Development of Lentigines?
The MC1R Gene
This gene contains instructions for the production of melanocortin-1 receptor. This receptor is activated by the Melanocyte Stimulating Hormone (MSH), one of the two hormones that regulate pigmentation. This receptor is mainly found on the surface of melanocytes, cells that are involved in melanin production. They are also found in certain immune cells of the body.
This receptor controls which form of melanin is produced by melanocytes. Normally, eumelanin, the lighter pigment, is produced, but when there are certain changes in this gene, pheomelanin, the darker pigment is produced by the cells.
Variations in this gene are associated with differences in hair and skin color. Several SNPs associated with the MC1R gene are primarily linked to fair skin, red or light hair, and freckles.
rs2228479
rs2228479, also called Val92Met or V92M, is an SNP found in the MCR1 gene. The A allele of this SNP is associated with a higher risk of developing sunspots.
It is also associated with an increased risk of sunburns and red hair.
The IRF4 gene
The IRF4 gene contains instructions for the production of interferon regulatory factor 4. These proteins are mainly involved in the body’s response to infection by viruses.
This gene is also found to be strongly associated with pigmentation, sensitivity to sun exposure, freckles, blue eyes, and brown hair color.
rs12203592
rs12203592 is an SNP found in the IRF4 gene.
The T allele is the risk allele and is associated with a higher sensitivity to sun exposure, freckles, and brown hair
The C allele is the protective allele and is associated with a lower risk of sunspots and melanoma.
Non-genetic Influences on Lentigines
Increased exposure to ultraviolet (UV) light
Exposure to UV light causes the skin cells to produce more melanin. This causes pigmentation and increases your risk of developing sunspots.
Indoor tanning
Tanning beds also increase your exposure to UV light and can influence the appearance of sunspots.
Phototherapy
Phototherapies like PUVA (psoralen and ultraviolet A) treatment used to treat eczema and psoriasis can lead to the appearance of PUVA lentigines.
Radiation therapy
Radiation therapy in the course of cancer treatment can also make you more likely to get lentigines.
Recommendation to Remove Lentigines
Lentigines are typically not harmful and are not a cause for medical concern. They do not have to be treated, but you can follow certain measures to lighten them.
Cryotherapy: Liquid nitrogen or nitrous oxide solution is used to freeze the sunspots. It only takes a few minutes.
Chemical peels: These can be a little painful and cause a burning sensation on your skin. This involves applying an acid solution on the sunspots that turns into a wound that peels off.
Laser resurfacing: A laser beam is used to remove the layers of skin under the sunspot. The area is allowed to heal for about 10-20 days, and new skin grows.
Intense Pulse Light (IPL): Pulses of light energy target the melanin and destroy it by heating, which results in the removal of the colored spots. This takes only about 30 minutes and causes very little to no pain.
Sunscreen: Sunscreen of SPF 50 or above can help prevent sun spots by protecting your skin from exposure to UV rays.
OTC products: Bleaching creams that contain hydroquinone or retinoids can be used to lighten the sunspots
Home remedies: Aloe vera, licorice extract, apple cider vinegar, green tea bags, lemon juice, milk, or honey can be used on the skin to lighten the sunspots.
Summary
- Lentigines, also called sunspots, are brown or black spots found on the skin, mainly in areas exposed to the sun. They are mostly irregular in shape and vary in size.
- Sunspots are not usually itchy and do not display any other symptoms. They are not of medical concern.
- MCR1 and IRF4 are two genes that are associated with the risk of developing sunspots. Both of these genes influence the regulation of skin pigmentation.
- Increased UV exposure, indoor tanning, phototherapy, and radiotherapy can also lead to the development of sunspots.
- Lentigines can be treated by using chemical peels, laser resurfacing, intense pulse light, and cryotherapy.
- Sunscreen can be used to prevent sunspots. Certain bleaching creams and home remedies can be used to lighten the existing sunspots.
References
https://www.healthline.com/health/lentigo#types
https://medlineplus.gov/genetics/gene/mc1r/#function
https://dermnetnz.org/topics/lentigo/
https://www.healthline.com/health/sunspots-on-face#risks
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3704782/
https://www.ncbi.nlm.nih.gov/pubmed/11487574
