Other pigmented birthmarks include Café-au-lait spots and Mongolian spots. Because they resemble the color of coffee with milk, Café-au-lait spots can appear anywhere on a child’s skin and may grow in number over time. A single Café-au-lait spot, it isn’t concerning, but if you discover a half a dozen or more that are bigger than a pencil eraser, or if they’re clustered in a single area, you should contact your pediatrician. That’s because they could be a sign your child has a genetic disorder called neurofibromatosis, which can cause abnormal cell growth of nerve tissues. Children with Asian, American Indian, African, Hispanic, or Southern European backgrounds often display Mongolian spots, which can be found usually on the lower back or the buttocks. They’re flat bluish gray patches, and they’re nothing to worry about.