Congenital dermal melanocytosis

  • Congenital dermal melanocytosis (formerly called Mongolian blue spots) are a type of birthmark. The term congenital dermal melanocytosis refers to one or more birthmarks.They are flat blue or blue/grey spots with an irregular shape that commonly appear at birth or soon after.

    Although they may look like bruises, it is important to recognise that congenital dermal melanocytosis are birthmarks, not bruises

    Congenital dermal melanocytosis are most common at the base of the spine, on the buttocks, back and shoulders.  They are extremely common among Asian children, as well as children with dark skin, including people of Polynesian, Indian and African descent.  

    Signs and symptoms of congenital dermal melanocytosis

    • Congenital dermal melanocytosis are bluish to blue-grey spots, which may resemble bruising.
    • The coloured area feels the same as normal skin to the touch.
    • They are most commonly found at the base of the spine, on the buttocks and back, and may cover a large area of the back.
    • Occasionally the spots can appear elsewhere on the body, like the shoulder. These tend to persist and are less likely to disappear.

    If your child has congenital dermal melanocytosis, they are otherwise healthy. The birthmarks are not associated with any other medical symptoms or illnesses, and do not cause any pain.

    Treatment for congenital dermal melanocytosis

    No treatment is needed or recommended. The spots do not cause any medical complications. The discolouration often fades within the first years of life, and the birthmarks have usually gone once the child reaches adolescence. Less than 3 per cent of cases will continue into adulthood, and these are usually the ones present in body sites other than the buttock and spine areas.

    When to see a doctor

    Most cases of congenital dermal melanocytosis do not need to be seen by a doctor, unless there is some doubt as to the type of mark your child has. If the spots are particularly large, growing or located near the mouth, then these should be reviewed by a paediatrician or paediatric dermatologist (skin specialist).

    Key points to remember

    • Congenital dermal melanocytosis are a type of birthmark, with flat blue or blue/grey spots.
    • They may resemble bruises but they are not bruises, they are birthmarks.
    • There are no medical complications associated with congenital dermal melanocytosis. 
    • No treatment is needed – they will usually go away by the time the child reaches adolescence.

    For more information

    • See your family doctor, paediatrician or dermatologist.

    Common questions our doctors are asked

    How can I tell if it's a bruise or a congenital dermal melanocytosis?

    Congenital dermal melanocytosis and bruises do look very similar, and the birthmarks are often mistaken for bruises. However, they are different in a few ways. Bruises change colour, size and shape over the course of just a few days, while congenital dermal melanocytosis stay the same for many years. Also, congenital dermal melanocytosis are not painful when touched. Congenital dermal melanocytosis are present from birth.

    What can I do if my child's congenital dermal melanocytosis is very prominent and is causing them embarrassment? Is laser treatment an option?

    We do not recommend any treatment for congenital dermal melanocytosis, as it is unnecessary because the birthmarks will fade over time on their own. Treatment, such as laser therapy, may cause side effects, including infection and scarring.

    Developed by The Royal Children's Hospital Dermatology department. We acknowledge the input of RCH consumers and carers.

    Reviewed August 2020.

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