What is a Mongolian spot?

A Mongolian spot is congenital dermal melanocytoses characterized as a congenital hyperpigmented spot found in the sacrococcygeal region. Most frequently found in black or Asian infants, it also occurs in infants of other races. The pigmentation often improves spontaneously in the first 3 to 5 years of life but may persist to some degree into adulthood. These lesions are believed to represent the delayed disappearance of dermal melanocytes. The deep blue pigmentation is another example of the Tyndall effect.

Snow TM: Mongolian spots in the newborn: do they mean anything? Neonatal Netw 24:31–33, 2005.