A 6 weeks old baby has a blue mark near coccyx since birth. His mother is worried. What would you do?

The key is A. Reassure. [This is a benign condition known as “Mongolian spot” or “Mongolian blue”. Mongolian spot refers to a macular blue-gray pigmentation usually on the sacral area of healthy infants. Mongolian spot is usually present at birth or appears within the first weeks of life. Mongolian spot typically disappears spontaneously within 4 years but can persist for life].