Mucosal Lentigines is a dermatitis condition that is characterized by the development of lesions with increased pigment due to excess melanin (natural skin pigment secreted by the body). These lesions are also known as macules which are of light brown colour and develop on mucosal surfaces. Lentigines (singular: lentigo) is a distinctive spot (named because they look like lentils in appearance) on the skin that is of darker shade (usually brown) as compared to the rest of the skin.
Histopathologically, these are present at the basal-epidermal junctions and vary in size from 15 to 20 mm. The pigment is constricted to the lower squamous epithelium. They are also called benign melanocytic tumours. These lentigines are more common in some patients suffering from Caucasian Disease (Disease that affects white people).
Lentigines are not only attributed to persons with fair skin, rather, but they may also inflict anyone. Different skin types exhibit different degrees of pigmentation e.g. dark-complexioned person shows hyperpigmentation in contrast to a lighter skin toned person. Moreover, these lentigines can affect any person regardless of gender.
A number of persons get affected by it but most commonly it appears in young adulthood, particularly in adolescence. They may increase in number with an increase in melanin pigment and diagnose on the basis of their appearance. Their number may vary depending upon the type of lentigo. In contrast to melanocyte nevus, lentigines do not make nests of melanocytes. They are diagnosed by dermatoscopy, biopsy and diagnostic excision.
Causes of Mucosal Lentigines:
The major cause of Mucosal Lentigines is excessive exposure to the sun. Lentigines often occur on the skin sites which remain revealed to the sun i.e. hands, face and feet. Some lentigines may develop as a result of genetics or due to radiation therapy. Moreover, you are more prone to lentigines if you have:
- Light skin complexion
- Suntanned (skin burned from UV radiations)
- Extreme exposure of skin to the sunlight
- Radiation therapy (phototherapy) and photochemotherapy (PUVA)
- Indoor tanning
Some inherited syndrome (autosomal dominant: Homozygous non-sexual chromosomal genes) may result in lentigines, for example, Cowden Syndrome, Peut-Jeghers Syndrome, Noonan/LEOPARD Syndrome, Bannayan-Riley Rubalcaba Syndrome, Myxoma syndrome (NAME, LAMB), and Xeroderma Pigmentosum. These syndromes are usually occurred due to the mutation in mTOR signalling, RAS-MAP kinase and PTEN pathways.
Site of occurrence of Mucosal Lentigines:
There is no specific site of their occurrence, for instance, they may appear or distribute at acral sites, genitals (genital melanocytes lentigines), nail bed, mucosal areas and lip (labial melanocytic lesions). Lentigines, most probably appear on the mucosal surfaces or the adjacent glabrous areas for example vulva, penis, anus (genital lentigines) and lips.
Some lentigines are limited to a single-segmented site with sharp discrimination in the center. A few of them appear on face, buttocks, sole and palm. These are called pattern lentigines and mainly can be seen in African people.
Genital tissues bear a higher density of melanocytes as compare to other body parts thus magnify the pigmentation. But this pigmentation may vary with different hormonal changes from adolescence to menopause. They also vary in size showing irregular borders. In men, they can vary from tan to brown lesions and appear on the corona/shaft and tip of the penis with a size of 15mm. In females, the size varies from 5 to 15mm and appears anywhere.
The labial melanocytic lesions are clinically diagnosed as a single, well defined circular, light brown lentigo. Such lentigo is relatively smaller than other genital and multiple lentigines and appears frequently on the lower lip.
Roughly, one of every 10 women has pigmented vulvar lentigo in her lifetime. According to research, almost 68% of vulvar pigmentations are lentigines which may vary from tan to black colour. Such pigmented macules contain melanin which is a colored compound naturally secreted in the body. Some of these are without melanin and filled with debris instead.
These lentigines are symmetric, having no change in consistency as compared to normal skin.
Because genital skin has more melanocytes as compare to extragenital skin, that’s why the biopsy threshold of genital pigmentation is lower. For such lentigines, an excisional biopsy is preferred rather than a shave biopsy. Dermoscopy is also performed for confirmation.
Valval lentigo most probably appears on perianal skin as well as on hair-bearing labia majora. Sometimes they appear on proximal medial thighs and show uniform pigmentation which fades with time. They are larger in size e.g. up to 2cm in diameter with irregular margins.
Vulvar melanosis shows various patterns such as reticular, structureless or ring-like patterns. Moreover, the patients suffering from lichen sclerosis (white patches on the genital skin) are at high risks of vulvar melanosis.
Types Of Lentigines:
Lentigines can be classified into various types on the basis of their cause and site of appearance.
1. Lentigo Simplex (Simple Lentigo)
It is a very common melanocytic macule (precise cause is unknown) that is small in size (round, oval, stellate shaped) and characterized by light melanocytic proliferation. It is seen in children and not related to sun exposure.
They are more stable sometimes producing dermal nests in the junctional zone and keep increasing in number slowly. Because they have progressive capacity thus considered the precursor of an acquired junctional melanocytic nevus with the passage of time. Its color is ranging from light to dark brown and lesion diameter is 5-15 mm with a clear-cut outline.
They usually start at birth or in childhood and may vanish with time. The simplex lentigines are more common in patients who have red hair and skin which is exposed to sunlight. They mostly occur on the trunk, legs, limbs and may be found anywhere on the skin as well.
“Labial melanotic macule” is a term that is now being used clinically for the lip lesions that were previously recognized as “lentigo simplex”.
2. Solar Lentigines:
Solar Lentigines are caused by excessive exposure to ultraviolet radiation from the sun. These particularly affect middle-aged people and elderly patients (over the age of forty). In contrast to lentigo Simplex, they are not single and are rather found in multiple numbers. These are usually considered the hallmarks of aged skin. That’s why they are often called the “age spots” or “liver spots”. They are found on the face, shoulders, arms, and hands because these skin parts remain exposed to the sun. These age spots can progress and grow with age and over time become darker.
Morphologically, they are short, bulb-shaped with finger-like projections extending deep into the skin. These appear dark brown to black lesions of 3 to 12 mm in diameter and are considered the cause of malignant melanoma in patients who suffer from xeroderma pigmentosum ( A genetic disease that culminates in severe sunburn).
Furthermore, these also result in freckles during adolescence. The genetic cause behind solar Lentigo is the excessive exposure to ultra-violet radiations in the past that may have changed the genetic makeup (mutation in the gene of melanocytes) producing more melanin and a decreased proliferation and differentiation of mucosal keratinocytes.
3. Inkspot Lentigo:
It is also called reticulated Lentigo. It is caused as a result of sunburn in people with the fair skin tone but is less in number as compared to solar lentigines. It appears as irregular dark brown to black ink like lesions. These ink spots are often one in number and mostly occur in patients of Celtic ancestry (Central Europe tribes). In past, it was mistakenly taken as malignant (Cancer causing). But now, it is considered the melanotic macule together with a genital and labial melanocytic nevus. Pigmented corneocytes (Cells in the outermost skin layer) are the characteristics of inkspot lentigo.
4. PUVA Lentigo:
This Lentigo occurs after “psoralen and ultra-violet A” (PUVA) therapy. This therapy is done for persons suffering from skin diseases e.g. Psoriasis and Eczema. It occurs on sun-protected (such as buttock) as well as on sun-exposed areas.
These lesions are 3 to 8mm in diameter and are confined on the body for 6 months after the completion of treatment. Some of these have a diameter of 3cm and remain for 2 years or more.
The persons working in tanning parlours can also experience such lesions although psoralen is not administered there. It is considered, somehow, similar to ink-spot lentigines. PUVA exposed dermis looks like freckles and shows melanocytic atypia.
5. Tanning bed Lentigo:
Such Lentigines appear when skin is exposed to an indoor tanning bed (also called sunbeds). These tanning beds are used as the source of vitamin D since people residing in that area don’t have enough natural sunlight as a possible source. Tanning bed lentigos range between 2 to 5 mm in diameter.
6. Scar Lentigo:
Scar Lentigo is a pigmented lesion that can give rise to melanocytic hyperplasia (increased number of melanocytes, which are the cells producing melanin pigment). Scar lentigo shows two different patterns, the one which induces epidermal hyperplasia (increased number or size of skin cells) and hyperpigmentation, while the other pattern only has melanocytic hyperplasia.
7. Radiation Lentigo:
It appears at the site where previously any radiation treatment was performed. Late-stage radiation, keratosis (growth of keratin in the skin), subcutaneous fibrosis (creates large lumpy masses) and epidermal atrophy (reduced thickness of the skin) is also associated with it.
8. Multiple Lentigines
They are also known as generalized lentigines and are not related to any syndrome. An old term “Lentiginosis profuse” is often used for multiple Lentigines. They may be induced as an eruptive phenomenon when there are no systematic abnormalities. They have a size between 5mm to 2cm and are widely spread on arms, genitalia and legs.
Treatment of Mucosal Lentigines:
Mucosal Lentigines are treated by using various procedures. These procedures are done alone or in combination for treating different kinds of lentigines. For example, Solar Lentigines are treated by using topical bleaching creams (retinoid/ hydroquinone), microdermabrasion (a technique used to renew the skin tone), Cryotherapy (freezing), chemical peels, vitamin C, azelaic acid, alpha hydroxy acid, laser (pigment lasers) and intense-pulsed light.
Picosecond lasers are being more popular regarding the treatment of this medical condition. Some modifications have been done in intense pulsed light sources and they are being effective in treating some kind of lentigines.
Treatment procedures are different for different patients based on their skin type and lesion color as well as multiple treatment sessions. Test treatments are more helpful in the clinical finding of treatment with the least side effects and more efficacy. Most sunscreens are used to prevent lesion reoccurrence or pigment alteration.
Frequently Asked Question
How to prevent lentigines?
To prevent lentigines, try to avoid sun exposure when the sunlight is at its peak hours i.e. 10:00 a.m to 2:00 p.m. Always use sunblock with SPF above 50, whenever you have to go outside. Wear sun-protective clothes and hats.
Who gets lentigines?
Lentigines may influence males and females and of any age without gender discrimination. But, solar lentigines can affect people with lighter skin color. Some lentigines that are related to other genetic syndromes may arise at birth or during childhood.
Do lentigines go away?
Although, lentigines resemble freckles yet freckles get fade in the winter season when sun exposure is less. In contrary to freckles lentigines don’t go away on their own. They need a proper treatment i.e. bleaching creams or intense lasers.
Can lentigines become malignant?
Lentigines may increase in number or get worse over time but they remain benign and don’t become malignant. But in 5% of cases, they can be transformed from benign to malignant.
What is the secondary care management of Lentigines?
The secondary care management for lentigines includes Cryotherapy, Picosecond lasers, Intense pulsed light and chemical peels.