Dermal melanocytosis is an umbrella term that encompasses several cutaneous lesions characterized by blue-gray pigmentation. The three classic variants include congenital dermal melanocytosis (formerly known as Mongolian spots), nevus of Ota, and nevus of Ito. Although these lesions share a similar morphology, they are unique in their distribution and natural course.

PATHOGENESIS

Melanocytes in the mid to lower dermis produce the melanin that, via a phenomenon known as the Tyndall effect, results in the characteristic blue-gray pigmentation of dermal melanocytosis. Shorter wavelengths of light, such as blue, are more scattered in the affected skin compared with the surrounding unaffected skin, whereas longer wavelengths (red, orange, and yellow) are less scattered in the affected areas (Gilchrest et al., 1977).

CLINICAL FEATURES AND NATURAL COURSE

Congenital Dermal Melanocytosis

Congenital dermal melanocytosis, is a gray-blue patch that commonly presents at birth or during the first few weeks of life (Figure 1; Gupta & Thappa, 2013). Although dermal melanocytosis affects both genders equally and can present in all races, it is more common in individuals of Asian or Black descent. Studies estimate the prevalence of dermal melanocytosis to be 81%-100% in Asian populations, 95.5%-96% in Black populations, 46.3%-70.1% in Hispanic populations, and 9.6% in white populations (Cordova, 1981; Jacobs & Walton, 1976; Leung, 1988).

FIGURE 1. Three distinct patients with congenital dermal melanocytosis showing the clinical spectrum of this benign condition.

Dermal melanocytosis primarily affects the lumbar and sacral regions but can involve other areas of the skin (Figure 1). It presents as a single or multiple macules or patches and typically involves <5% of the body surface area (Franceschini & Dinulos, 2015). The color varies from light blue to blue-gray. The cutaneous lesions commonly fade by the age of 1 or 2 years and rarely persist past the age of 6 years (Onayemi et al., 2001). Extrasacral locations of dermal melanocytosis are less common and include the lower or upper extremities, groin, shoulder, or chest. These lesions are less likely to show full clearance (Onayemi et al., 2001).

Dermal melanocytosis is a benign condition diagnosed clinically. Extensive dermal melanocytosis may be associated with lysosomal storage disorders, such as GM1 gangliosidosis Type 1, Hunter syndrome, and Hurler syndrome (Mimouni-Bloch et al., 2016). Alternatively, multiple large spots could also be indicative of phakomatosis cesioflammea or phakomatosis cesiomarmorata (Thomas et al., 2016).

In rare instances, some lesions may appear after birth. These can be confused for bruises or child abuse. The features differentiating dermal melanocytosis from bruising include nontenderness to palpation, typically present at birth, and no changes over a short period (Prasad & Tully, 2017). Child abuse should be suspected when bruising is seen in children who are not mobile or infants, bruising is seen outside bony prominences, there are multiple bruises of uniform shape in clusters, or there are bruises with an imprint. Specific sites of bruising that should raise suspicion for physical child abuse include bruises to the face, back, abdomen, arms, buttocks, ears, or hands (Maguire et al., 2005).

Nevus of Ota

Nevus of Ota is a blue to blue-gray facial lesion that typically presents unilaterally and follows the distribution of the ophthalmic (M1) and maxillary (M2) divisions of the trigeminal nerve (Franceschini, 2015). Affected areas may include the conjunctiva, sclera, periorbital regions, forehead, temple, earlobe, or nose and malar area. If scleral involvement is present, there is an increased risk of glaucoma and elevated intraocular pressure (Franceschini, 2015). Similar to dermal melanocytosis, nevus of Ota predominantly affects darker pigmented individuals. Nevus of Ota has a bimodal distribution of onset, presenting during infancy or at the onset of puberty. Nevus of Ota persists lifelong and can be progressive. Nevus of Ota can be complicated by ocular melanoma (Chan et al., 2000), so routine follow-up with an ophthalmologist is recommended.

Nevus of Ito

Nevus of Ito presents as a single or multiple blue to blue-gray macules and patches in the supraclavicular, scapular, and deltoid regions. Clinically and histologically, there is no difference between nevus of Ota or nevus of Ito. Nevus of Ito also persists lifelong and can be progressive. Melanoma is a much rarer complication in nevus of Ito (Tse et al., 2016).

TREATMENT

Persistent lesions can be managed with cosmetic treatments including cover-up or laser therapies. The bulk of the literature focuses on the treatment of nevus of Ota, although similar protocols can be adapted for the treatment of other variants of dermal melanocytosis as well. Laser therapies of choice include the Q-switched (QS) ruby (694 nm), the QS alexandrite laser (755 nm), and the QS neodymium-doped yttrium aluminum garnet laser (Nd:YAG; 532 and 1062 nm) as these target the chromophore melanin (Shah et al., 2016). Treatment with QS alexandrite lasers is done at 2- to 3-month intervals, whereas treatment with QS Nd:YAG laser is done at 2- to 3-week intervals with an average of 17 sessions for near-total improvement (Shah et al., 2016). QS ruby and QS alexandrite are recommended for fair skin and are associated with hypopigmentation and hyperpigmentation, whereas QS Nd:YAG lasers are recommended for darker skin and are associated with risks of epidermal damage and patient discomfort (Shah et al., 2016). More recent case studies have aimed at using picosecond lasers over nanosecond lasers to reduce the number of treatment sessions (Williams et al., 2021).

CONCLUSION

Congenital dermal melanocytosis is a common birth mark that fades over time. Lesions in extrasacral locations do not always show full clearance. Extensive involvement can raise suspicion for an underlying systemic disorder. Dermal melanocytosis is associated with three different subtypes (congenital dermal melanocytosis, nevus of Ota, and nevus of Ito) that differ in the lesion location, onset, and duration. In select lesions, treatment can be considered using QS ruby, QS alexandrite, or QS Nd:YAG lasers.

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