It is present at birth and typically disappears spontaneously within 4 years. The Mongolian spot is a congenital, developmental condition exclusively involving the skin. It results from entrapment of melanocytes in the dermis during their migration from the neural crest into the epidermis. This condition is most common among Asians. No sex predilection exists.
Mongolian spots consist of blue-gray macular pigmentation.
Typically, it is a few centimeters in diameter, although much larger lesions also can occur. Most commonly, it involves the lumbosacral area, but the buttocks, flanks, and shoulders may be affected in extensive lesions. Aberrant Mongolian spots involve unusual sites such as the face or extremities. Persistent aberrant Mongolian spots also are referred to as macular-type blue nevi. Mongolian spots have been associated with cleft lip, spinal meningeal tumor, melanoma, and phakomatosis pigmentovascularis.