Basics
Formerly known as chloasma, melasma, or the “mask of pregnancy,” is an acquired form of hyperpigmentation arising most often on the face.
It is rare before puberty and most commonly occurs in women during their reproductive years, particularly those who have darker complexions and live in sunny climates.
Melasma is seen in Asia, the Middle East, South America, Africa, and the Indian subcontinent. In North America, it is most prevalent among Hispanics, African-Americans, and immigrants from countries in which it is common.
It may appear during pregnancy, from oral contraceptive use, during menopause, or it may arise de novo for no apparent reason.
When men are affected, the clinical and histologic picture is identical; however, the explanation for this condition in males is unknown.
Clinical Manifestations
Primarily a cosmetic problem consisting of asymptomatic, blotchy darkening of the facial skin.
Lesions are found mainly on the cheeks, angles of the jaw, forehead, nose, chin, and above the upper lip (Fig. 23.10).
The hyperpigmentation often follows the rim of the zygomatic arch and the nasolabial fold is generally spared (Fig. 23.11).
Lesions are tan to brown, hyperpigmented macules that may coalesce into symmetric, well-demarcated patches.
During pregnancy, the darkening of the skin often occurs in the second and third trimesters and most often spontaneously fades after termination of pregnancy.
Melasma also tends to fade on discontinuance of oral contraceptives or avoidance of sunlight; however, it may persist indefinitely.
Postinflammatory Hyperpigmentation (see the Discussion below) Solar Lentigines (“Liver Spots”)
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Differential Diagnosis
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Management
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Helpful Hints 
SEE PATIENT HANDOUT Basics
Darkening of the skin may occur after nearly any inflammatory eruption, such as eczema (Figs. 23.12 and 23.13), lichen planus, acne, or after an injury to the skin such as a burn. Elective skin treatments (e.g., chemical peels, laser resurfacing, or dermabrasion) may also precipitate postinflammatory hyperpigmentation.
The hyperpigmentation stems from the melanocyte's exaggerated response to cutaneous insult, which results in an increased or abnormal distribution of the pigment melanin.
As with melasma, postinflammatory hyperpigmentation tends to develop more often in people with dark complexions.
Clinical Manifestations
As in postinflammatory hypopigmentation (discussed above), this is an asymptomatic cosmetic issue.
Lesions tend to conform in location and shape to the preceding eruption or injury (Fig. 23.14A,B).
Phytophotodermatitis and Berloque Dermatitis 
Basics
Phytophotodermatitis is a phototoxic reaction that results from contact with a photosensitizing agent followed by sun exposure.
Photosensitizing chemicals are called furocoumarins and are commonly found in several citrus fruits and plants, including lemons, limes, bergamot oranges, grapefruit, celery, parsley, parsnip, and hogweed.
The reaction is a chemically induced, nonimmunologic, acute skin reaction requiring light (usually within the UVA spectrum; i.e., 320 to 400 nm).
A botanical cause for dermatitis is suspected when the pattern of an eruption is linear or streaky, such as noted in the contact dermatitis caused by poison ivy (see Chapter 13: Eczema and Related Disorders).
When the phytophotodermatitis is caused by perfume or other agents such as oil from the bergamot lime (Citrus bergamia), an ingredient in some perfumes and fragrances, it is referred to as berloque dermatitis.
Clinical Manifestations
The initial skin response resembles an exaggerated sunburn which may be accompanied by blisters (Fig. 23.15A). The reaction typically begins within 24 hours of exposure and peaks at 48 to 72 hours.
Postinflammatory hyperpigmentation that may last several weeks or longer typically ensues (Fig. 23.15B).
Poikiloderma of Civatte
Clinical Manifestations
Lesions consist of erythema associated with a mottled pigmentation located on the sides of the neck and other sun-exposed areas.
The shaded submental and submandibular areas are usually spared, supporting chronic sunlight exposure as the apparent cause of this condition (Fig. 23.16).
Confluent and Reticulated Papillomatosis (Gougerot-Carteaud Disease)
Clinical Manifestations
CARP is characterized by hyperkeratotic papules and plaques that coalesce to form hyperpigmented, confluent plaques centrally with a reticular pattern peripherally (Fig. 23.17).
CARP is usually located on the trunk, back, lateral or posterior neck or the flanks (Fig. 23.18).
Diagnosis
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Basics
Acanthosis nigricans (AN) has a characteristic hyperpigmented skin pattern that occurs primarily in flexural folds. The skin is thought to darken and thicken in reaction to circulating growth factors and insulin resistance.
The majority of cases of AN, including idiopathic cases and those associated with obesity, are referred to as benign AN.
Other benign forms of AN are associated with endocrine disorders, such as insulin-resistant diabetes, polycystic ovary syndrome, Cushing disease, Addison disease, pituitary tumors, pinealomas, and hyperandrogenic syndromes with insulin resistance.
AN is sometimes related to drug use, most commonly secondary to glucocorticoids, nicotinic acid, diethylstilbestrol, or growth hormone therapy. AN may also be inherited without any disease associations.
The rare, so-called malignant AN is associated with an internal malignant disease, usually an intra-abdominal adenocarcinoma. Affected patients generally have a poor prognosis. The skin condition is sometimes seen before the cancer is recognized; it can also be associated with recurrences and metastases.
Clinical Manifestations
AN generally presents with a gradual evolution of symmetric, asymptomatic, tan or brown to black, leathery or velvety plaques.
Plaques are sometimes “warty” (papillomatous) and studded with skin tags.
They have linear, alternating, dark and light pigmentation that becomes more apparent when the skin is stretched (Fig. 23.19).
The most common sites of involvement are the axillae, the base of the neck, the inframammary folds, the inguinal areas, and the antecubital fossae (Fig. 23.20).
The dorsa of the hands (especially the knuckles), the elbows, and the knees are also common locations.
Less commonly, mucous membranes, the vermilion border of the lips, and the eyelids are involved.
Points to Remember Basics
Carotenemia is characterized by yellow pigmentation of the skin caused by an increased level of beta-carotene in the blood. Most cases result from prolonged and excessive consumption of carotene-rich foods, such as carrots, squash, and yams (sweet potatoes).
Less commonly, carotenemia has been associated with diabetes mellitus and hypothyroidism.
Clinical Manifestations
The yellow-orange pigmentation often first appears on the palms and soles (Fig. 23.21).
The tip of the nose, the nasolabial folds, the palate, and other areas of the skin may become involved.
The sclerae are spared, which distinguishes carotenemia from jaundice.
Outline