Hyperpigmentation is the increase in the natural color of the skin. Melanin,a brown pigment manufactured by certain cells in the skin called melanocytes,is responsible for skin color. Melanin production is stimulated by a pituitary hormone called melanocyte stimulating hormone (MSH). Other pigments appearin the skin much less often. Melanin gives skin its natural color.
Darkened spots on the skin come in several varieties. The most ominous is malignant melanoma, a very aggressive cancer that begins as an innocent mole. Most moles (nevus), however, are and remain benign (harmless). The average person has several dozen, and certain people with a hereditary excess may have hundreds. Freckles, age spots, and cafe au lait spots, known as ephelides, are always flat and not as dark. Cafe au lait spots are seen mostlyin people with another hereditary disorder called neurofibromatosis. "Port wine stains" are congenital dark red blotches on the skin. Other common dark colorations on the skin are called keratosis and consist of locally overgrownlayers of skin that are dark primarily because there is more tissue than normal. A few of these turn into skin cancers of a much less dangerous kind than melanoma.
Darkened regions of the skin occur as a result of abnormal tanning when the skin is sensitive to sunlight. Several diseases and many drugs can cause photosensitivity. Among the common drugs responsible for this uncommon reaction are birth control pills, antibiotics and diuretics, nonsteroidal anti-inflammatory drugs (NSAID), pain relievers, and a couple psychoactive medications. Some of the same drugs may also cause patches of discolored skin known as localized drug reactions and representing an allergy tothat drug. Sunlight darkens an abnormal chemical in the skin of patients with porphyria cutanea tarda. Several endocrine diseases, some cancers, and several drugs abnormally stimulate melanocytes, usually through an overproductionof MSH. Arsenic poisoning and Addison's disease are among these causes. A condition known as acanthosis nigricans is a velvety darkening of skin in folded areas (armpits, groin, and neck) that can signal a cancer or hormone imbalance.
Of particular note is a condition called melasma (dark pigmentation of the skin), caused by the female hormone estrogen. Normal in pregnancy, thisbrownish discoloration of the face can also happen with birth control pills that contain estrogen.
Overall darkening of the skin may be due to pigmented chemicals in the skin.Silver, gold, and iron each have a characteristic color when visible in the skin. Several drugs and body chemicals, like bilirubin, can end up as depositsin the skin and discolor it.
There are a number of other rare entities that color the skin, each in its own peculiar way. Among these are strange syndromes that seem to be birth defects and vitamin and nutritional deficiencies.
The pattern of discoloration is immediately visible to the trained dermatologist, a physician specializing in skin diseases, and may be all that is required to name and characterize the discoloration. Many of these pigment changesare signs of internal disease that must be identified. Because pigmentation changes may also be caused by medication, the drug responsible for the reaction must be identified and removed.
Skin sensitive to sunlight must be protected by shade or sunscreens with an SPF of 15 or greater. Skin cancers must be, and unsightly benign lesions may be, surgically removed. Laser surgery is an effective removal techniquefor many localized lesions. Because it spreads so rapidly, melanoma should be immediately removed, as well as some of the surrounding tissue to prevent regrowth.
Sunlight is the leading cause of dark spots on the skin, so shade and sunscreens are necessary preventive strategies, especially in people who burn easily.