Hyperpigmentation
Hyperpigmentation is one of the major skin changes by photo-aging (UV radiation). Hyperpigmentation comes in many forms. Hyperpigmentation is a general term used to describe any darkened area of the skin caused by an increased production of the skin pigment, melanin. Hyperpigmentation can affect nearly all skin types, all ages, men and women. Typically, those with darker skin tones are more prone to hyperpigmentation issues as their skin tones normally have more melanin. Often hyperpigmentation is only a cosmetic issue, but it can also be the result of an underlying medical condition which could require professional care.
Hyperpigmentation comes in the form of a dark age spot (also called liver spot), scars, or brown/red patches on the skin. Age spots can come in many different shapes and sizes, but interestingly enough they also come with different names. Some people call them sun spots, others refer to them as liver spots. They can also be known as lentigos, or senile/solar lentigines. But ultimately, all these terms refer to the same thing – those red/brown spots on the skin typically found on the hands, face, shoulders, arms, forehead, and the head if bald.
Age spots are usually harmless and are only a cosmetic concern. The spots are caused by years of sun exposure and consequently are typically found on areas of the body that are the most exposed to sunlight. Age spots are usually found on men and women over the age of 40 mainly due to the skin’s diminishing ability to regenerate itself after sun exposure. In some cases, cancerous growths can be mistaken for harmless age spots
Melanocytes manufacture the pigment melanin. Melanin is what gives our skin its color. Melanocytes appear as small cells, usually in or near the stratum basale. They have thin cytoplasmic processes (not evident in ordinary histological preparations) which extend between nearby keratinocytes and serve to transfer melanosomes (melanin-containing granules) into adjacent keratinocytes. Because of this transfer, most pigment-containing cells in the epidermis are normally keratinocytes rather than melanocytes. Melanocytes are derived from neural crest and migrate to their final position in the epidermis. This developmental propensity for travel may contribute to the dangerously metastatic potential of melanomas.
Melanin forms through a series of oxidative reactions involving the amino acid tyrosine and the enzyme tyrosinase. Tyrosine is the immediate precursor to melanin. Enzyme tyrosinase is the rate-limiting, essential enzyme in the biosynthesis of the skin pigment melanin in melanocytes. The body must contain tyrosinase and copper to be able to use tyrosine to create melanin.
The first step is the most critical because the remainder of the reaction sequence can proceed spontaneously at physiological pH. Here, tyrosinase converts tyrosine to dihydroxyphenylalanine (DOPA) and then to dopaquinone. Subsequently, dopaquinone is converted to dopachrome through auto-oxidation, and finally to dihydroxyindole or dihydroxyindole-2-carboxylic acid (DHICA) to form eumelanin (black-brown pigment). The latter reaction occurs in the presence of dopachrome tautomerase and DHICA oxidase. In the presence of cysteine or glutathione, dopaquinone is converted to cysteinyl DOPA or glutathione DOPA. Subsequently, pheomelanin, a yellow-red pigment, is formed.
More importantly melanin protects our skin from the sun’s UV radiation. When the skin is exposed to the sun, its natural defense is to create more melanin, causing an overall darkening or tanning. While tanning is considered natural and often associated with beauty, the side effect of excessive tanning is often not as pretty. When the skin becomes damaged, either by too much sun, an external injury or by some internal cause, it can respond by creating excessive pigment and forming a pronounced dark spot or discoloration. These discolorations are referred to as hyperpigmentation and can come in the form of a dark age spot, scars, or brown/red patches on the skin.
Determining the cause of the hyperpigmentation is important in selecting the best approach for treatment. Based on the history and clinical findings of the patient, the causes of the hyperpigmentation may include postinflammatory hyperpigmentation, drugs, photosensitizing agents, ultraviolet light, or systemic disease (eg, Addison disease, liver disease, pregnancy, pituitary tumors).
Hyperpigmentation can also be caused by many different medical illnesses such as Addisons and Cushings disease, Melasma, Linea Nigra, Tinea, Celiac Disease and more. For this reason, it is important that a doctor fully diagnose the individual before he/she attempts to treat just the cosmetic symptoms.
Hyperpigmentation can often be successfully treated with the use of skin lightening creams. Many of these creams contain an ingredient called hydroquinone which is a chemical skin lightener that can be used in various concentrations ranging from 2%-10%. Over the counter hydroquinone creams are available in a maximum of 2% concentration. Some active ingredients of a lightening cream have the ability to block tyrosinase which in turn block the conversion of precursor tyrosine to melanin. Laser treatments (Q-switched laser) and cryotherapy are also available for the treatment of age spots.
The sun is the worst enemy of hyperpigmentation. Without proper sun protection, it is nearly impossible to expect successful treatment. The best way to prevent age spots is by practicing proper sun protection with the use of protective clothing and sunscreens.