Final answer:
Mongolian spots are bruise-like marks that can appear on the buttocks of African-American newborns. They are caused by a concentration of pigmented cells in the skin and typically fade away on their own within a few years.
Step-by-step explanation:
African-American newborns may have bruise-like marks on their buttocks called Mongolian spots. These spots are blue or gray and are caused by a concentration of pigmented cells in the skin. They are more common in babies with darker skin tones and usually fade away on their own within a few years.