A birthmark (or nevus, the plural form is nevi) is a skin marking that is present at birth or appears within a few weeks of birth. Birthmarks can occur anywhere and they are very common in infants. Most are harmless, but sometimes they can be associated with other health problems. Talk to your doctor about whether this might be the case for your child.

What Causes Nevi?

No one knows what causes birthmarks to occur; despite numerous “legends,” they are not caused by anything that was done or not done during pregnancy.

Diagnosis & Treatment of Nevi


There are two main types of nevi: pigmented and non-pigmented. It is important to note that vascular lesions can also appear either at birth or within the first year of life. These are not nevi, but appear because blood vessels in your child’s skin are not formed correctly.


These birthmarks are the result of an overproduction of pigmentation in the skin.

Congenital (moles): These are patches of skin that may be light brown in fair-skinned children and may be almost black in darker-skinned children. They’re usually raised. They’re found on the head and neck 15% of the time but may occur anywhere on the body. They may appear in a variety of sizes, including some that are very large (giant nevi). There is a small chance that pigmented nevi can turn into skin cancer (melanoma) over time, and your doctor may ask that either these lesions be watched carefully or surgically removed.

Café au lait spots: These flat, tan spots (which are the color of coffee with milk) can appear anywhere on your child’s body. They’re completely harmless, but if your baby has several of them and they’re larger than a quarter, it’s a good idea to have your child evaluated for neurofibromatosis (a genetic disorder).

Mongolian spots: These large, blue-gray birthmarks are often found on the lower back or buttocks and look like bruises. They’re completely harmless and usually fade without any treatment by the time the child is school age.


Nevus sebaceous: These lesions appear at birth as a yellow-tan plaque, and are most commonly located in the scalp. After puberty, these lesions tend to become raised and thickened, and often become more visible and irritated. A small number of these lesions can go on to develop forms of skin cancer (usually basal cell cancer). Your doctor may ask that these lesions be surgically removed to prevent skin changes and possible skin cancer in the future.

Verrucous epidermal nevus: These lesions appear as areas of raised, irregular skin texture at birth. In darker skinned individuals the lesions may look pigmented. These lesions are often difficult to distinguish from nevus sebaceous. They sometimes take on an inflammatory component and can be sources of considerable skin irritation and itching. Surgical removal and skin resurfacing are often used, particularly in those lesions that present with itching and inflammation.

Vascular Lesions

Hemangiomas: These are the most common vascular birthmarks. They typically appear within one to two weeks of birth and grow rapidly during the first few months of life. They usually shrink back and disappear by the time a child is five to nine years old.

Most of the time, they cause no problems, but complications can occur if their location interferes with sight, feeding, breathing or other functions.

Port-wine stains: These are flat stains that range from a pale pink color to a deep wine red. They usually appear on a child's face or neck and eventually may become thick or develop small ridges or bumps. They don’t fade with age.

Though port-wine stains are not dangerous, they can be disfiguring and embarrassing for children. Lasers are the best treatment. Most of the stains lighten after several treatments with a "pulsed-dye" laser, although some return and need re-treatment. Laser treatment is often started in infancy when the stain and the blood vessels are smaller.

Macular stains (“salmon patch,” “angel's kiss” or “stork bite”): These are pinkish birthmarks that appear on your child’s forehead, eyelids or neck. The skin is not thickened and feels no different from anywhere else on the body. Nearly half of all babies have such a birthmark. They usually fade significantly by the time your child is two years old and don’t require any treatment.

Giant Nevi

A nevus may be described as giant if it covers a large portion of a newborn’s major anatomical area, such as on the head, trunk, legs or arms. Another way to describe it is that it covers more than 2% of the patient’s total body surface area, or is larger than the palm of the child’s hand.

A giant nevus is usually accompanied by a number of additional smaller nevi, called satellites. When a child is born with a giant nevus, it is common for satellite nevi to be present at birth.

If the lesion is small enough, the nevus can be removed in stages. However, the child’s skin can be grown to replace the nevus if it’s large. A common way of developing more tissue to cover the area from which the nevus will be removed is through tissue expansion.

In this procedure, the skin and soft tissues adjacent to the giant nevus are stretched to grow new skin. If tissue expansion is performed, a balloon — called an expander — is placed under the child’s skin, typically near the nevus so that a flap of skin can be created. Over a period of several weeks, the expander is filled with more and more liquid to gradually stretch the skin around it. When enough extra skin has been created, the tissue expansion is complete, and the new flap of skin is used to replace the nearby nevus.

Tissue expansion can be done practically anywhere on the body, and your child’s doctor will determine the best area for the expander balloon to be placed. Some common areas for tissue expansion are in the thigh, back, abdomen and scalp.

There are alternative ways to resurface the giant nevus, and these include skin grafts harvested from an uninvolved area, flaps of tissue transferred from nearby areas or microvascular transfer of skin and tissues from other parts of the body. Your doctor will discuss all of the possible options with you to determine which method will be the best for your child.

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