WHAT IS HYPERPIGMENTATION
Hyperpigmentation is a term that means more pigmentation, that is darker areas or patches of skin as compared to the rest of the skin of a particular individual. Hyperpigmentation is not dark skin color per se, and those with darker skin tones are not said to be hyperpigmented! The term hyperpigmentation (also called hypermelanosis) implies that in one individual there are areas, spots, or patches of skin that are significantly darker than the normal skin tone of that individual.
SKIN PIGMENT – MELANIN
The skin contains cells in its outer layer (epidermis) called melanocytes that produce the skin pigment melanin. Excess melanin production can lead to hyperpigmentation.
Melanin pigment is of 2 types: the darker eumelanin (black-brown) and the lighter pheomelanin (red-yellow). The vital step in the formation of melanin is the conversion of the amino acid tyrosine to Dopa by the enzyme tyrosinase. Many drugs used to treat hyperpigmentation inhibit this step or enzyme.
Melanin is usually present inside granules called melanosomes. However, overproduction of melanin can lead to increase in free melanin being deposited in the skin epidermis and dermis that gives a relatively darker (hyperpigmented) appearance. Also, larger and denser melanin granules give a much darker appearance.
SUN EXPOSURE AND MELANIN PRODUCTION
Melanin, especially eumelanin protects the skin from the harmful effects of the ultraviolet (UV) rays of the sun, and also has anti-inflammatory and anti-oxidant effects.
UV rays comprise of UVA and UVB. Both stimulate melanin production. UVA has less energy and more penetration as compared to UVB. Therefore, UVA is associated more with a generalized increase in melanin production like tanning, and long-term skin aging. UVB in small amounts is needed for vitamin D synthesis, but too much exposure can cause sunburn as an immediate effect, and increase the risk of skin cancers as a long-term effect.
With more exposure to the sun, more eumelanin is produced in response to stimulation by UV rays, and the darker the skin appears. Therefore, people living closer to the equator have darker skin tones. The ratio of eumelanin to pheomelanin is not only determined by sun exposure but also by genetic and other environmental factors.
INFLAMMATION AND HYPERPIGMENTATION
Skin injury and inflammation are strong stimulators of melanin production. This is the reason that areas of skin that have suffered severe inflammation, prolonged constant itching, injury, and/or scarring often become hyperpigmented (PIH- Post Inflammatory Hyperpigmentation). Inflammatory mediators in the skin can cause a drastic increase in melanin production, leading to large amounts of dense large melanosomes and free melanin getting deposited in the lower epidermis as well as the deeper dermis. This can make hyperpigmentation long-term and sometimes very difficult to treat.
CAUSES OF HYPERPIGMENTATION
Skin inflammation
It is the most common cause of localized patches of hyperpigmentation. This could be due to massive and prolonged itching as seen in eczema, lichen planus, allergies, acne, reactions to chemicals, injuries, and burns.
UV rays from sun exposure
This is the most commonly attributed cause for dark spots like sunspots (solar lentigines), age spots (senile lentigines), and other hyperpigmented patches on sun-exposed areas of the body.
Melasma
Melasma is an acquired, hyperpigmentation disorder characterized by more or less symmetrically distributed, medium to dark brown patches (macules), affecting the sun-exposed areas, particularly the cheeks, nose, upper lip, chin, forehead, and temples. It is more common in women. The butterfly distribution of the hyperpigmentation on the cheeks is characteristic. Melasma is sometimes assessed by scoring the extent and intensity of the face area involved (Melasma Area and Severity Index -MASI score).
UV exposure causing increased melanin synthesis and accumulation, is the most common postulated cause. However other contributory factors can include hormonal imbalance due to contraceptives or pregnancy (melasma during pregnancy is called chloasma), genetic factors, and cosmetic use. Melasma is not a serious condition, but since it affects appearance, it can have a great psychosocial impact on the affected individual.
Other causes of hyperpigmentation
These include certain chemotherapy drugs and radiation exposure, autoimmune disorders like lupus or SLE (systemic lupus erythematosus), hormonal imbalances (seen in pregnancy, oral contraceptive use in women), prolonged cosmetic use, and smoking. People who have conditions like diabetes or hyperthyroidism may also show hyperpigmented spots. Hyperpigmentation is seen in Addison’s disease, a rare hormonal disorder of the adrenal glands located just above the kidneys. Acanthosis nigricans is a skin condition causing dark discoloration in the body folds and creases, seen more commonly with obesity.
Note: Hemochromatosis is actually an iron overload disorder and gives a greyish discoloration (not to be confused with hyperpigmentation).
Nevi
A melanocytic nevus (plural: nevi) or brown/black mole, is a benign skin condition due to a local increase of melanocytes. It can be present at birth (congenital nevus) or appear later (acquired nevus) and can be present on the skin in any area of the body. These nevi may be genetic or familial and are usually persistent through life if present from early childhood, while those acquired in adolescence or adulthood are mainly due to sun exposure and may show fading with time.
Congenital nevi can range from small size (<1.5cm) to large ones (giant melanocytic nevus) >20cm. The nevi may also appear as brown spots called Café au lait patches, or be speckled or hairy. A Mongolian spot is a large bluish nevus often seen on the buttocks of a newborn, while nevus of Ota refers to oculo-dermal melanosis (hyperpigmentation involving eye and face).
Usually, nevi do not need treatment. Congenital giant or multiple nevi if present are observed for any suspicious changes in color, texture, or size that may indicate a need to investigate for skin cancer (melanoma risk 0-5%). Such nevi or others that are unsightly or inconvenient may be removed by excision/shave biopsy, and by laser or electrosurgery.
Becker’s nevus is a large, brown hyperpigmented patch occurring mostly in males, typically occurring on one shoulder and upper trunk. It is usually first noticed while approaching puberty but can present earlier as well. It is benign, is not known to have malignant potential, and needs no monitoring or treatment except for cosmetic purposes when a laser is sometimes done.
TREATMENT
The treatment of hyperpigmented patches is often very challenging and the results can be disappointing. It also takes many weeks to months of persistent treatment to see visible results. Usually, hyperpigmentation in areas other than the face is rarely treated, and is not of much consequence. However, hyperpigmentation on the face or melasma is treated to improve cosmesis. There are several substances that have been studied to decrease pigmentation and have shown variable results in clinical trials. Several skin lightening creams are available with a combination of such substances.
SUNSCREENS
These should be applied especially when going out during the day. Sunscreens should be selected according to the condition and should protect adequately against both UVA and UVB.
Read: Sunscreen-Important Points
SKIN LIGHTENING CREAMS
The three most effective agents that are used in the initial aggressive management of hyperpigmentation and melasma are hydroquinone, tretinoin (a retinoid), and a corticosteroid (like mometasone, fluocinolone). These are often available as the triple combination cream, and should only be used under the guidance and monitoring of a doctor, preferably a dermatologist. Hydroquinone and tretinoin are inhibitors of the action and synthesis respectively of the tyrosinase enzyme, which mediates the crucial step in the production of melanin. Corticosteroids act by suppressing inflammation and the activity of melanocytes. If used indiscriminately, hydroquinone can cause a speckled pigmentation (called ochronosis), while tretinoin can cause dryness and irritation. Corticosteroids can cause topical steroid-damaged/dependent face (TSDF), a recognized entity comprising of face redness, thinning of the skin, stretch lines, and acne. Therefore, these creams should not be used as general fairness cream or excessively without medical supervision.
Other milder agents reducing hyperpigmentation are often part of over-the-counter skin lightening creams. Kojic acid, tetrahydrocurcumin (THCC), and arbutin are substances that have tyrosinase inhibiting and anti-inflammatory properties thus decreasing melanin synthesis. Other such agents include retinol (a milder retinoid than tretinoin), azelaic acid, and niacinamide. The efficacy of these agents is not proven to be that significant, therefore they are best used in milder cases, or as long-term maintenance treatment after the initial triple combination use. Other herbal combinations without much clinical evidence used in such creams include licorice, aloe vera, bearberry, and green tea extracts. Antioxidant substances also prevent stimulation of melanin synthesis due to UV-mediated skin damage. These include vitamin C and E, and glutathione.
EXFOLIATING AGENTS
These are acids of low concentration like 1-2% glycolic and salicylic acid that help to remove the superficial layers of the epidermis and thereby the melanin deposited in it along with dirt, debris, and dead cells. This helps to make the face look a shade lighter, while the skin lightening agents do their work of inhibiting further melanin production.
COSMETICS
These include various foundations, concealers and make-up items that have no therapeutic value but help to improve appearance. One should be careful in selecting such items so that they do not end up causing skin reaction or irritation thereby worsening the situation. Testing these cosmetics on a small area is suggested before general use on the face.
PROCEDURES
These procedures should only be performed by experienced and trained dermatologists. They are considered in those patients who are not showing response to treatment with the mentioned skin lightening agents especially those with resistant melasma and post-inflammatory hyperpigmentation. As mentioned even though hyperpigmentation is not a serious condition, its psychosocial impact may be significant. These procedures may require multiple sessions and mainly work by removing layers of the affected skin. Skin lightening creams are sometimes continued alongside, with close medical observation. The procedure itself can sometimes cause inflammation and pigmentation if used inappropriately or without experience and training.
The procedures for hyperpigmentation include:
- Chemical peels – These are higher concentration acids like glycolic acid 20–70%, lactic acid 40-70%, salicylic acid 10-30%, and trichloroacetic acid TCA 35-50%)
- Laser therapy – These include Q-switched ruby laser, low-dose Q-switched neodymium-doped yttrium aluminum garnet laser, fractional erbium-doped fiber laser, fractional CO2 lasers, picosecond-domain Nd: YAG lasers
- Intense pulsed light (IPL) – This uses high-intensity pulses of visible light
- Microdermabrasion – A special applicator with an abrasive surface or fine particles of aluminum oxide or sodium bicarbonate with a suction, is used to gently remove the thick outer layer of the skin.
Also read –
10 Important Causes of Light Skin Patches (Hypopigmentation)
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References:
Evidence-based treatment for Melasma