Congenital Dermal Melanocytosis (Formerly Mongolian Spots)

Congenital dermal melanocytosis, formerly called Mongolian spots, are bluish-gray birthmarks that appear soon after birth. If this birthmark appears, it usually appears on your baby’s lower back and butt. It’s easy to mistake them for bruises, but they aren’t.

Healthcare providers no longer call this birthmark a “Mongolian spot” because the name didn’t accurately reflect who can have them.

These birthmarks are harmless, don’t need treatment and may fade as your child grows.

Types of congenital dermal melanocytosis

There are three types based on when the birthmark goes away:

• Common: It fades in infancy.
• Extensive: It needs longer to fade, usually middle childhood.
• Persistent: It lasts into adulthood.

What does congenital dermal melanocytosis look like?

Features of this birthmark are:

• Blue, purple, gray, greenish or darker patches on your child’s skin
• Flat areas that feel smooth, not raised
• One spot or several spots in the same area
• Round, oval or uneven shapes

Congenital dermal melanocytosis causes

This birthmark forms while a fetus is still developing in the uterus. It happens when some melanocytes (the cells that give skin its color) don’t move to the surface of the skin as they normally do.

During early pregnancy, these cells form deep within the skin. Usually, they move up to the surface before your baby is born. In babies with this birthmark, some of the cells stay deeper in their skin instead. Healthcare providers aren’t sure exactly why this happens.

These deeper cells still make skin color (pigment). But because they’re under the surface, the color looks bluish-gray. This effect happens because of how light reflects off the deeper pigment in your child’s skin.

Risk factors

While anyone can have these spots, they’re more common in babies with Asian, Black or Hispanic ancestry.

Even though it’s rare, very large patches or widespread involvement can associate with a genetic metabolic disorder. These are conditions that you get from your biological parents. They affect how your body breaks down and stores certain substances.

Examples include:

• GM1 gangliosidosis
• Hunter syndrome
• Hurler syndrome
• Mannosidosis
• Mucolipidosis
• Niemann-Pick disease

How doctors diagnose congenital dermal melanocytosis

Doctors diagnose this birthmark with a physical exam. The exam typically happens when your baby is born or at their first checkup. They usually don’t need a biopsy or other tests to confirm it. If tests are necessary, it’s often because the birthmark covers a large area of skin and there’s concern for an underlying condition.

As these spots mimic bruises, your child’s healthcare provider will take notes of the birthmark’s size and shape. They may also take a photo of the birthmark so it’s clear that it’s harmless and not caused by an injury or abuse.

How is congenital dermal melanocytosis treated?

Your child won’t need treatment for skin affected by dermal melanocytosis. The color may darken temporarily during infancy and fade gradually with age. If the spot doesn’t fade, talk with your healthcare provider. They may suggest laser therapy to help lighten the color. But this is optional and only for cosmetic reasons. It’s not necessary to treat.

How long does congenital dermal melanocytosis last?

Most of these birthmarks fade over time. Many disappear during your child’s first year, and the majority are gone by age 6 to 10. In some cases, they may last into adulthood. Spots are more likely to last if they’re darker or larger than 10 centimeters. Every child’s skin is different, so how long the spots last can vary.