Newborn Skincare

The most common birthmarks you may see in your baby (and when to be concerned). Part I

Most are harmless but some require further work-up for underlying defects or for the dreaded possibility of cancer.

Ah, birthmarks. Almost all of us have them, and they usually represent a cute little feature that makes us unique. However, birthmarks in infants can be very concerning to parents. Will they get bigger? Will it affect my child’s social and emotional development? Does it represent something more dangerous? These are important questions that will be discussed in this article.

Most birthmarks can be divided into two major groups: pigmented (related to skin color) and vascular (related to blood vessels). Most are harmless but some require further work-up for underlying defects or for the dreaded possibility of cancer. In this article we will discuss pigmented ones and in part II we will discuss vascular ones.

Congenital melanocytic nevi (moles)

Congenital melanocytic nevi also known as moles occur in 1-2 percent of infants at birth. Scientists believe they arise when melanocytes (the cells that form the pigment that gives our skin color) fail to migrate to their appropriate final location. They usually appear as flat dark brown to black patches but some can be raised.

Large congenital nevi (moles) are at a risk of transforming into melanoma.

Congenital melanocytic nevi are challenging because there is a risk of melanoma arising within them. For example, one study showed that melanoma developed in 0.5 to 1 percent of patients. The average age at diagnosis of melanoma was about 15 years old. So, while the vast majority are totally harmless, regular visits to the dermatologist are absolutely essential to look for dangerous changes that could indicate a melanoma. The estimated final size of the lesion in adulthood is the best predictor for development of melanoma. Lesions expected to be larger than 40 cm in adulthood having the highest risk of cancer transformation. Large lesions (final size predicted to be 20 to 40 cm) occur in about 1 in 40 newborns and have about a 5 percent chance of converting into melanoma at some point during the child’s life. Another risk factor for transformation into melanoma is a large number of “satellite” nevi (smaller pigmented spots) nearby the big one.

Congenital nevi will almost certainly change as your baby grows. However, always remember the “ABCDE” rule. Any pigmented spot that is A) asymmetrical B) has irregular borders, C) changing in color D) larger than a pencil eraser or E) evolving in any way, needs to be evaluated immediately. Changes in color, shape, or thickness, particularly, warrants further evaluation. Surgical removal of high-risk nevi is a decision best made with the counsel of a pediatric dermatologist, but doesn’t always mean that your baby is in the clear. Recurrence at the original site is possible, and another melanoma could arise at a different site. Therefore, patients should be followed regularly by an experienced dermatologist, whether the mole is removed or not.

Dermal melanosis

Dermal melanosis is a very common kind of pigmented birthmark. They are commonly called “mongolian spots”, and usually appear as flat blue-gray or brown-black lesions caused by pigment cells that are trapped deep within the skin. They are usually found on the back or buttocks and can sometimes be confused for bruises or even child abuse. They are much more common in black, Asian, and Hispanic babies than in white ones. These spots will fade by around two years of age and do not require any treatment.

Mongolian spots fade with age and do not require treatment.

In part II we will finish up our discussion with blood vessel based birthmarks!


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