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KEY POINTS
Pigmentary demarcation lines are normal boundaries of the skin that represent a transition between levels of melanin pigment in the skin corresponding to dermatomal innervation.
Longitudinal melanonychia is a normal pattern of nail pigmentation seen in patients with skin of color. It is important to differentiate normal nail pigmentation from malignant melanocytic proliferations and extraneous pigment deposition.
Physiologic pigmentation of the oral mucosa is commonly seen in patients with skin of color.
Erythema dyschromicum perstans is seen more often in people with skin of color.
Lability of pigment in the darker-skinned population causes dramatic changes in skin color after inflammatory processes of the skin.
Many common dermatologic conditions manifest with follicular or papular lesions in dark-skinned individuals.
Keloidal scarring is common in patients with skin of color.
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NORMAL VARIATIONS IN SKIN OF COLOR
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The skin can provide diagnostic evidence of either local or systemic disease. Therefore, when evaluating pigmentation, it is important to understand and recognize normal variants.1 Knowledge of normal variations in skin is crucial in the evaluation and management of patients with skin of color because there are a number of skin lesions that represent physiologic variants. Historically, the lack of recognition of benign variations in dark skin has led to unnecessary treatment and potentially poor results. These lesions fall into pigmentary and nonpigmentary categories.2
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Pigmentary Demarcation Lines
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Pigmentary demarcation lines are normal boundaries of the skin that represent a transition between darker and lighter melanin pigment distribution corresponding to dermatomal innervation by spinal nerves. There are six types of pigmentary demarcation lines based on anatomic location3 [Table 21-1]. In one study, 79% of African American women and 75% of African American men had at least one pigmentary demarcation line. These lines may be present at birth, arise later in life, or occur during pregnancy.4
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Type A lines, also termed Voigt (Futcher) lines, are sharply demarcated, frequently bilateral lines of pigmentation found at the anterolateral junction of the upper arms [Figure 21-1]. The change from darker to lighter pigment occurs at the junction of the extensor to flexor surface of the arm. Type B lines occur at the posteromedial aspect of the lower legs and often arise during pregnancy.5 Up to 14% of black women present with type B lines during pregnancy.4 Other pigmentary demarcation lines ...