02/20/2026
Derm Index: Insights into Mongolian Spot
Mongolian spots, also known as dermal melanocytosis, are a common and generally benign pigmented skin lesion observed in newborns. These birthmarks are characterized by blue-grey, green-blue, or brown discolorations of the skin, typically found on the sacral-gluteal region or the shoulders. Dermal melanocytosis is especially prevalent in infants of Asian, Native American, and some African descent, but they can also occur in infants from other racial groups. These lesions are often temporary, with many fading during childhood, although some may persist into adulthood.
Clinical Presentation
Dermal melanocytosis usually appears at birth or within the first few weeks of life and is most commonly located on the lower back, buttocks, or shoulders. In some cases, multiple lesions may appear in close proximity, although they rarely involve the head, face, or flexural surfaces of the extremities. The spots are typically flat, round, or oval-shaped, and can range in size, with some lesions reaching up to 10 cm in diameter. The characteristic color of dermal melanocytosis is attributed to a blue-grey or greenish hue, which is the result of the Tyndall effect. This phenomenon occurs when light is scattered by the deep dermal melanocytes, which are normally found in the basal layer of the epidermis but in this case are located deeper in the dermis.
Dermal melanocytosis is clinically benign and is not associated with melanoma or other forms of skin cancer. They often resolve spontaneously over time, typically fading or disappearing by the age of 2 to 4 years. However, in some cases, the lesions may persist longer or even remain throughout adulthood.
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