What are those Brown Spots on my Baby?

In the weeks following the birth of your baby you may start to notice brown spots on his body. These are often called café au lait spots. They can be fairly large in size—from the size of a dime to the size of a baseball. You can see them on any part of a baby’s body, and often there are more than one.

Café au lait spots appear in as many as 25% of babies. Most have one to three of these spots. They are totally harmless—as long as there are fewer than six of them.

Neurofibromatosis

If your child has more than six café au lait spots that are bigger than 5 millimeters in diameter (or 12 millimeters after puberty), he may have neurofibromatosis Type 1. This disease also causes benign (non-cancerous) tumors called neurofibromas to grow near nerve tissue. For example, the eye or optic nerve may have a growth. These growths can interfere with function, such as eye sight. Another way to tell if a person has neurofibromatosis is to look at the bones on an x-ray as they may look abnormal.

If one parent has neurofibromatosis, it generally gets passed down to the children. And believe it or not, neurofibromatosis occurs in one out of three thousand people so it is quite possible you know someone or will meet someone with it.

People with neurofibromatosis need to be followed closely by multiple doctors to be sure these neurofibromas are not growing along any nerve that will interfere with function. The disease evolves over time, and so doctors follow these patients carefully.

Café au lait spots are extremely common in babies and children and should not be a worry unless there are more than six. As far as I know, having a few café au lait spots doesn’t increase a person’s risk of skin cancer or other cancers.

Café au lait versus Mongolian spots

Don’t confuse café au lait spots with Mongolian spots. Mongolian spots are also hyperpigmented, flat spots that can appear anywhere but usually occur in the lower spine area. They are dark black and blue and look more like a bruise. Mongolian spots occur more commonly in Asian populations and people of color and, like café au lait spots, are totally harmless.

So, if you see a new spot on your baby that fits the description of a café au lait spot or Mongolian spot, do not be alarmed. View it as just another way for you to identify your baby.

Dr. Victoria McEvoy graduated from Harvard Medical School in 1975 and is currently an Assistant Professor of Pediatrics at HMS. She is the Medical Director and Chief of Pediatrics at Mass General West Medical Group. She has practiced pediatrics for almost thirty years. She has been married to Earl for thirty six years and raised four children. She currently enjoys writing, traveling, reading, almost all sports, and spending time with her two grandsons.

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