MBS CDM The most common location is the sacral-gluteal region, followed by the shoulders They rarely occur on the head, face, or flexor surface of the extremities.

The most common location is the sacral-gluteal region, followed by the shoulders [31]. They rarely occur on the head, face, or flexor surface of the extremities.

Congenital dermal melanocytosis is completely benign and usually fades during the first or second year of life [35]. By 6 to 10 years of age, the vast majority has disappeared. However, approximately 3 percent remain into adulthood, particularly those in extrasacral locations.

The lesions result from the delayed disappearance of dermal melanocytes.

Congenital dermal melanocytosis should be distinguished from other lesions that do not fade, such as blue nevi, nevus of Ota, or nevus of Ito

Extensive dermal melanocytosis with a ventral as well as dorsal distribution that is persistent and/or progressive in nature has been reported in at least 40 children with various lysosomal storage diseases [38-40]. (See "Inborn errors of metabolism: Classification", section on 'Lysosomal storage disorders'.)

●Clinically apparent dermal pigmentation of the perioral area has been described in up to 20 to 50 percent of patients with cleft lip, implying a common pathogenic defect in migration of cells from the neural crest [41].

In phakomatosis pigmentovascularis type II, aberrant Mongolian spots are seen in association with capillary malformations (port-wine stains)