A 5-month old infant is brought in for routine visit. What is the probable cause for the following findings?

The image shows congenitsl dermal melanocytes (Mongolian spot) It is the most frequent encountered pigmented lesion in newborns Mongolian spots are completely benign Congenital dermal melanocytosis typically appears as blue-gray pigmented macule with indefinite borders, although it also can be greenish-blue or brown The diameter of the lesion may be 10cm or more The most common location is the sacral-gluteal region, homogenous gray-blue patches is usually diagnostic, paicularly when located in classic sites, there are repos of false accusations of child abuse resulting from misinterpretation of congenital dermal melanocytosis as bruises (which tend to change color and resolve more quickly) Ref: Nelson textbook of pediatrics 21st edition Pgno: 868