These are blue or slate-grey macular lesions (previously called a Mongolian blue spot) with variably defined edges, seen most commonly over the pre-sacral area.
They may be solitary or numerous and can involve large areas.
More than 80% of Afro-Caribbean and Asian infants have them compared with <10% of Caucasian infants. Malignant degeneration does not occur.
Reference: Kleigman, R. M., Behrman, R. E., Jenson, H. B., Stanton, B. F. (2007). Nelson Textbook of Pediatrics. 18th Ed. Elsevier/Saunders.
Previously published: 23/10/14