White : Diseases of the Skin - Pigmentary Disorders

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Gary M. White & Neil H. Cox

Diseases of the Skin

21	Pigmentary Disorders

PIGMENTARY CONDITIONS THAT ARE NORMAL OR COMMON IN DARKER-SKINNED PATIENTS

Overview of dermatology in darker skin

There are few structural differences between black and white skin. The number of melanocytes is the same, although the number and arrangement of melanosomes differs. There are fewer elastic fibers in the dermis, a factor that (along with spiral-shaped hair follicles in those of African-Caribbean extraction) has been implicated in some hair disorders.
    The increased pigment in black skin provides photoprotection and reduces skin cancer incidence (albino people living in the tropics have a huge skin cancer problem). It also masks erythema and thus may make diagnosis of inflammatory dermatoses more difficult. Note that the same problem occurs with reading patch tests.
    A number of conditions occur that are specific to darker skin, or that have altered frequency or presentation in darker skin; some of the commoner or most important examples are listed in Table 21.3. Many of these are discussed more fully in this section or elsewhere. It should be remembered that some of these reflect cultural practices rather than ethnicity or skin color per se, and some estimates of frequency are influenced by economics and use of healthcare services.
    This section covers selected pigmentary conditions that are normal or common in darker-skinned patients. The emphasis is on black skin, but there are also several disorders that are commoner in Asian skin, both pigmentary (e.g. Mongolian spot, nevus of Ota, and nevus of Ito; Ch.31) and others (e.g. Ofuji disease and Kimura disease).

Table 21.3 SOME SKIN DISORDERS THAT ARE ALTERED IN DARKER-SKINNED PATIENTS

Type of disorder	Examples	Comments
Normal pigmentary variants	Longitudinal melanonychia Pigmentary demarcation lines Localized hypopigmentation Pigmented gums Hyperpigmented, hyperkeratotic elbows in dark-skinned patients Dermatosis papulosa nigra Patterned inherited lentiginosis of blacks	Some also occur in paler skins but are less obvious, for example pigmentary demarcation lines
Disorders of scalp or hair and/or of cultural hair treatments	Pseudofolliculitis barbae Acne keloidalis nuchae Dissecting folliculitis or cellulitis of scalp Traction alopecia Trichophyton tonsurans infection Pomade acne Increased contact allergy to para- phenylenediamine (PPD) black dye Hair breakage due to hair relaxing agents or ‘hot comb’ alopecia	See text, this chapter Chapter 10 Chapter 28 Chapter 28 Chapter 26 Chapter 10 Probably due to use of darker shades with greater PPD content Reflects overuse
Other cosmetic product-related problems	Steroid acne or striae Pigmentary disturbance Reduced contact allergy to formaldehyde and releasers	Steroids may be used in illicit skin-lightening or 'blemish removal' creams Patchy pigment loss or, paradoxically, acquired ochronosis due to hydroquinone in skin-lightening creams Probably due to greater use of ointments and less of creams, which mainly contain these preservatives
Some disorders in which pigmentary disturbance may be pronounced	Atopic dermatitis Pityriasis alba Lichen planus Acne Pityriasis versicolor Any depigmenting disorder Any postinflammatory hypo- or hyperpigmentation	Hyper- and hypopigmentation; see Chapter 6 and text in this chapter Hypopigmentation Hyperpigmentation Hyperpigmentation Hypopigmentation For example, vitiligo is more obvious Any such change is exaggerated in black skin
Some disorders that may present differently or that require specific consideration in black skin	Psoriasis, dermatitis, urticaria, and other inflammatory dermatoses Lichen planus Infections Pityriasis rosea Sarcoidosis	Erythema is difficult to appreciate Hypertrophic form commoner, less oral lesions Need to consider unusual organisms, also HIV, in those visiting endemic areas; pale areas due to leprosy may be easier to diagnose Inverse pattern is common More common, and forms of the disease differ from those in white skin (see text this chapter and Ch. 11)
Other normal variants and disorders that are specific to or are commoner in black skin	Keloid scarring Leukoedema Punctate keratosis of palmar creases Infundibulofolliculitis of Hitch and Lund Ainhum Facial African-Caribbean childhood eruption (FACE) Sickle cell disease ulceration Systemic lupus erythematosus Atopic dermatitis Other childhood disorders	Chapter 22 See text, this chapter See text, this chapter See text, this chapter See text, this chapter A differential diagnosis of acne, Chapter 10 Chapter 13 In some people of color resident in developed countries; Chapter 6 Transient neonatal pustular melanosis, infantile acropustulosis
Disorders that are less common in black skin	Melanocytic nevi Port wine stain Photoaging changes Skin cancers due to sunlight damage, see Chapter 32	Note, however, that some skin cancers may occur withrelatively higher frequency (e.g. plantar acrolentiginous melanoma) or at relatively unusual sites (e.g. basal cell carcinoma affecting genital skin)

Fig. 21.28 Normal intraoral pigmentory variation of skin color. (a) This pigmentation of the gums is present at birth and is quite common. (b) Pigmented fungiform papillae of the tongue. Black pigmented papilla of the tongue, most common in dark-skinned patients, may occur.

Fig. 21.29 Hyperpigmented, hyperkeratotic elbows.

Fig. 21.30 Patterned inherited lentiginosis of blacks.

Longitudinal melanonychia

These multiple, lightly pigmented bands are not of clinical concern. However, a solitary, new, dark band deserves further investigation (see Ch. 29).

Pigmentary demarcation lines

Etiology and pathogenesis

Pigmentary demarcation lines most commonly occur in dark-skinned patients but have also been described in East Asian and even white people. Some authors have expanded the classification of pigmentary demarcation lines to include those without a sharp transition from light to dark. Both Voigt lines and Futcher lines are terms that have been used to describe these changes. One theory suggests that the purpose of pigmentary demarcation lines is protection. The dorsal skin is more heavily pigmented to provide the skin with better protection from the sun.

Clinical

The most common pigmentary demarcation lines are those that appear as an abrupt transition between lighter and darker skin on the anterior portion of the upper arms (Fig.21.26). A similar change may occur on the posterior legs. In both, the darker skin is lateral and the lighter skin is medial.

Treatment

Pigmentary demarcation lines have no clinical significance other than cosmetic considerations. No treatment is needed or known to be effective.

Localized hypopigmentation

The concept of pigmentary demarcation lines has been expanded by some authors beyond the classic types to include hypopigmented areas where an abrupt transition is not seen. Midline hypopigmentation is quite common, occurring in approximately one-third of dark-skinned adults. White people may also rarely be affected. Well-defined hypopigmented patches running from the middle third of the clavicle to periareolar skin occur in approximately 13-16% of adult black patients (Fig.21.27). Posterior medial changes in pigmentation are the least common of these pigmentary alterations, occurring in fewer than 10% of black adults. Such lesions may occasionally be thought to represent vitiligo.

Fig. 21.31 Leukoedema. A pearly opalescent appearance of the buccal mucosa is common in darker-skinned patients. It is entirely benign.

Pigmented gums

Pigmentation of the oral mucosa is common in darker-skinned people (Fig.21.28). Various studies have found it in approximately 75-100% of black patients, from infants to adults. It is most commonly seen on the gingivae, but may also occur on the hard palate, buccal mucosa, and tongue. A band-shaped brownish pigmentation that runs horizontally just above the gingiva is common in Asian children. No treatment is needed or usually done, but periodontists have reported success with a process similar to dermabrasion.

Hyperpigmented, hyperkeratotic elbows in dark-skinned patients. This benign condition is similar in appearance to acanthosis nigricans (Fig. 21.29).

Dermatosis papulosa nigra

These pigmented papules of the face and neck are variants of seborrheic keratosis (see Ch. 30). Patterned inherited lentiginosis of blacksThe patient with patterned inherited lentiginosis of blacks has a striking lentiginous pigmentation of the central face and lips without mucous membrane or internal involvement (Fig.21.30). Lentigines may also be seen elsewhere (e.g. the buttocks or elbows). Inheritance is autosomal dominant. The appearance may resemble Peutz-Jeghers syndrome, Carney complex, and other syndromic lentiginoses, but no internal abnormalities are found. No treatment is usually needed, but the 510-nm dye laser may be used if necessary.