Congenital dermal melanocytosis (syn. Mongolian spots)

Congenital dermal melanocytosis is a blue-grey marking of the skin that usually affects the lower back and buttock region of newborn babies.

This chapter is set out as follows:

• The blue/black or slate-brown colouring results from dermal melanocytosis - the presence of functional melanocytes in the dermis. These cells have failed to reach their proper location in the basal layer of the epidermis during embryonic migration from the neural crest

• Mainly found in babies of East Asian ancestry, occuring less frequently in other races
• Normally present at birth

Distribution

• Lumbo-sacral region
• Extra-sacral lesions are occasionally associated

Morphology

• Poorly circumscribed patches of blue/black or slate-brown pigmentation
• Size - vary from a few cms to being very extensive

• Provide a patient information leaflet

• Lesions are sometimes mistaken for bruises and non-accidental injury

• They are benign and for most lesions reassurance is normally all that is required with fading in early childhood

• Patients with atypical presentations, eg, extending outside of the lumbo-sacral region and/or more than one lesion, should be referred to a Paediatric Dermatologist as further investigations may be required