The birthmark, which is called Mongolian spot, appears as a purplish mark on many newborns on the buttocks and lower back. The Mongolian spot, also known as congenital dermal melanocytosis, becomes visable at birth or during the first weeks of life. It tends to grow for the first two years but gradually disappears over time.
In most cases, it is completely gone by the time the child turns 10. However, if the spot does not fade by adulthood, it is called persistent Mongolian spot.
How and why does it occur?
The spot has a similar incidence in both sexes but varies among different racial groups. It is very common on Asian children (hence the name), occurring in over 90% of newborns. The spots affect about 80% of the African American population, while the frequency on white Europeans or Caucasians is less common, affecting less than 10% of the population.
Mongolian spots appear at birth or during the baby’s first weeks. They usually disappear after the first year but can persist until the teen years. However, it is uncommon to see them on school-aged children. Even if they are very pigmented and visible, there is no recommended treatment.
The color of the spot depends on the group of melanocytes present on the deep layers of the skin. Melanocytes are pigment cells that give the skin color. For this reason, Mongolian spots are not cancerous and are not associated to any condition. It is usually located on the lower back and buttocks but it can also cover a large portion of the back.
No special test is required to identify the spots. The doctor can diagnose the condition by examining the skin. Since there is no risk or connection to any disease, treatment is unnecessary if Mongolian spots are diagnosed as regular birthmarks.