Multiple and superimposed Mongolian spots.

To cite: Musumeci ML, Lacarrubba F, Santagati C, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/bcr-2013200740 DESCRIPTION A 3-week-old Asian male newborn (42 weeks gestation, normal spontaneous vaginal delivery) presented for evaluation of multiple congenital greyish-blue macules. Dermatological examination showed a large grey to light-grey patch with undefined edges involving the sacrococcygeal and gluteal areas (size 9×6 cm); within this lesion, a superimposed, dark-blue, coin-shaped spot was observed (figure 1). Moreover, a small (size 1×1.5 cm) round greyish-blue patch was present on the right arm (figure 2). A diagnosis of multiple and superimposed Mongolian spots (MS) was made. The parents denied consent for a cutaneous biopsy. MS, also known as congenital dermal melanocytosis, are benign, congenital, single or multiple bluish macules that usually affect healthy newborns and generally disappear during childhood. Although they are commonly observed in some racial/ethnic groups such as Asians and Native Americans, the presence of superimposed macules, as in our case, is a remarkable finding that has previously been very rarely reported. 2 Differential diagnosis mainly includes physical abuse, a condition excluded in our patient. As MS are histologically characterised by spindle-shaped melanocytes within the dermis, they are thought to be the result of the failure of melanocytes to correctly migrate from the neural crest to the developing epidermis. 4 In our case, the simultaneous presence of the large light-grey patch and the superimposed small dark-blue spot might be due to two different waves of melanocytic migration resulting in a different amount of dermal melanocytes in the two areas. Alternatively, dermal melanocytes in the superimposed spot might have arrested more superficially during embryogenesis.