+++
CONDITIONS MISTAKEN FOR PHYSICAL AND SEXUAL ABUSE*
++++
*The authors acknowledge the special contributions of Binita R. Shah, MD, to prior edition.
+++
CONGENITAL DERMAL MELANOCYTOSIS
++
Congenital dermal melanocytosis (also referred to as Mongolian spots or blue-gray macules of infancy) is the most frequently encountered birthmark in neonates. Melanin-containing melanocytes in the dermis are present (migrational arrest), and the distinctive blue color, characteristic of dermal melanin, occurs as a result of the Tyndall effect (when light strikes the surface of the lesion, red wavelengths of light are absorbed and blue wavelengths are reflected back from the brown melanin pigment from the dermis). Mongolian spots are more prevalent in Asian (40% to >80%), African American (30% to >60%), Hispanic (25%–70%), and Native American infants than in white infants (<10%). The skin lesion is flat (macular), slate-gray, greenish-blue or brown, and consists of poorly circumscribed, single or multiple lesions ranging in size from a few millimeters to several centimeters. The most common location are the sacrum and buttocks (90%), but lesions may occur anywhere, including the back, shoulders, or flank. Mongolian spots fade gradually and resolve by age 5 to 6 years in about 96% of cases. Differential diagnosis of Mongolian spots includes accidental or inflicted injury and other forms of dermal melanocytosis (eg, nevus of Ito or Ota; See Figures 2.13, 2.14, 2.15).
++++++++