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Mongolian spots (also referred to as blue-gray macule of infancy) are the most frequently encountered birthmarks in neonates. Melanin-containing melanocytes in the dermis are present (migrational arrest) and the distinctive blue color, characteristic of dermal melanin, occurs as a result of the Tyndall effect (when light strikes the surface of the lesion, red wavelengths of light are absorbed and blue wavelengths are reflected back from the brown melanin pigment from the dermis). More than 95% of African American and 80% of Asian infants are born with Mongolian spots. The skin lesion is flat (macular), slate-gray, bluish-gray or brown, and consists of poorly circumscribed, single or multiple lesions ranging in size from a few millimeters to several centimeters. The most common location is the sacrum and buttocks (90%), but lesions may occur anywhere, including the back, shoulders, or flank. Mongolian spots fade gradually and are resolved by age 5 to 6 in about 96% of cases. Differential diagnosis of Mongolian spots includes accidental or inflicted injury and other forms of dermal melanocytosis (eg, nevus of Ito or Ota).
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Emergency Department Treatment and Disposition
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Mongolian spots do not lead to any symptoms and require no treatment. Family needs to be reassured about the benign nature of these lesions.
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Mongolian spots can be mistaken for ecchymosis resulting from inflicted injuries. Mongolian spots are nontender unlike ecchymosis, which may be tender.
An ecchymotic skin lesion undergoes sequential color changes and resolves within a few days, whereas Mongolian spots do not undergo similar color changes and fade spontaneously over a period of years.
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