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DERMAL MELANOCYTOSES (BLUE LESIONS)

Etiology and pathogenesis

The pigmentation of nevomelanocytic nevi, lentigos, café au lait spots, etc. results from melanocytes in the epidermis. In contrast, dermal melanocytic lesions such as nevus of Ota and Ito, and Mongolian spots, result from melanin-producing cells in the dermis (Table 31.6). The blue color that characterizes these lesions results from the Tyndall effect (i.e. the scattering of light of shorter wavelengths as it passes through the skin).

PRACTICE POINTS

Nevus of Ota

The nevus of Ota is a facial dermal melanocytic lesion most common in Asian individuals. The age of onset is bimodal, with the larger peak at birth or soon after and the smaller peak at adolescence. Nearly all lesions appear by age 30 years. The incidence in the Japanese population has been estimated to be from 0.1 to 0.2%. Females predominate.

    It is characterized by a unilateral, blue-black or brown pigmented patch in the distribution of the trigeminal nerve (predominantly V1 and V2; Figs 31.84 and 31.85). This usually corresponds to the forehead, temple, eyelid, nose, ear, and scalp. Pigmentation may also be found in the oral mucosa, sclera, or tympanic membrane. Ocular involvement may take the form of hyperpigmentation of the sclera, iris, conjunctiva, choroid, or optic disc. Rarely, ocular, cutaneous, or intracranial melanoma may be associated.

    The Q-switched ruby and the Nd:YAG laser have been used effectively to treat such lesions. In a study of 522 patients from China, the Q-switched alexandrite laser gave satisfactory results in all patients, none of whom developed scarring. Usually, multiple treatments are needed.

Acquired bilateral nevus of Ota-like macules

Acquired bilateral nevus of Ota-like macules are grouped brown macules found along the temples of Asian or darkly pigmented women. In a
series of 320 patients, no affected men were found. In almost every case, appearance is after 20 years of age. Blue-brown or slate-gray macules distributed symmetrically on the cheeks, forehead, temples, eyelid, or nose are characteristic of this disease (Fig.31.86). The lesions are bilateral, in contrast to the most common presentation of nevus of Ota. When nevus of Ota is bilateral, mucosal and conjunctival pigmentation is usually seen.

Figure 31.82 (a) LEOPARD syndrome. The patient is covered with hundreds of pigmented macules. The larger lesions seen on the buttocks deserve close inspection and possible removal. The patient needs a complete history and physical examination plus an electrocardiogram. (b) LEOPARD syndrome, close-up view.

Figure 31.83 Carney complex. Blue nevi, as shown here on the ear, are part of this condition.

Figure 31.84 Nevus of Ota in an adult woman. This lesion may be covered with opaque make-up. Alternatively, laser treatment may be considered.

    Camouflage is the usual approach. Q-switched ruby laser combined with topical bleaching pretreatment has given good to excellent results, with a low occurrence of postinflammatory hyperpigmentation.

Figure 31.85 (a,b) Nevus of Ota in a young Hispanic girl. Note the extension to the ears and neck, and the scleral pigmentation.

Figure 31.86 Nevus of Ota–like macules. This condition is common in the East Asian woman and may be confused with sun damage.

Figure 31.87 Nevus of Ito. Note the small, blue macule on this young girl’s back.

Nevus of Ito

The nevus of Ito is a dermal blue patch, sometimes appearing to be a coalescence of macules, unilateral on the back or shoulder, and present since birth or early childhood (Fig.31.87). The classic situation involves the skin innervated by the posterior supraclavicular and lateral brachial cutaneous nerves. This lesion is less common than the nevus of Ota. It seems likely that the same lasers effective for the nevus of Ota would be effective therapeutically, although studies documenting this have not yet been published.

Mongolian spot

Etiology and pathogenesis

The Mongolian spot presents as a blue-black patch on the sacrum or buttocks of a neonate. Some have suggested changing the name to blue-gray macule of infancy to avoid using the term Mongolian. The incidence of this lesion varies greatly among the races, darker-skinned races having the highest incidence.

Clinical

A congenital blue-black patch on the sacrum is most characteristic (Figs 31.88 and 31.89). The color may be greenish-blue, blue-gray, or brown. The shape is often irregular and the borders indistinct. The size may range from a few millimeters to covering most of the back. Although the sacrum and buttocks are affected most often, the upper back, shoulders, or extremities are potential sites (Fig.31.90). The color often reaches a peak at 1–2 years and then begins to fade. The majority of these lesions are gone by adolescence.

Differential diagnosis

The diagnosis is usually obvious, and a biopsy is not needed (see Table 31.6 for the differential diagnosis of a blue patch). Confusingly, some clinicians have used the term ‘macular’ blue nevus to describe congenital, persistent blue patches outside the sacral area. However, blue nevi are small lesions, usually acral, and with some induration on palpation, while Mongolian spot and the other lesions discussed earlier are purely macular. Rarely, a Mongolian spot is misdiagnosed as representing the sequela of trauma (e.g. child abuse).

Treatment

No treatment is needed for this benign condition.

Figure 31.88 The Mongolian spot is found on the sacrum or low back at birth and tends to fade, often disappearing completely within a few years.

Figure 31.89 Mongolian spots. Multiple, extensive lesions are seen in this child. They were congenital and ?xed.

Figure 31.90 Mongolian spot. Many babies are born with a bluish patch on the sacrum. The majority of such lesions fade over time.

White/Cox: Diseases of the Skin, 2ed.(c) 2006, Elsevier Inc. All rights reserved.