Congenital dermal melanocytosis

What are the aims of this leaflet?

This leaflet has been written to help you understand more about congenital dermal melanocytosis. It tells you what it is, what causes it, what can be done about it, and where you can find out more about it.

What is congenital dermal melanocytosis?

Congenital dermal melanocytosis is a common, harmless, pigmented birthmark. Formerly, it was known as Mongolian blue spot. Sometimes, it is also called lumbrosacral dermal melanocytosis. It is usually seen at birth or shortly afterwards. It typically disappears before the age of 6.

What causes congenital dermal melanocytosis?

During the baby’s development in the womb, cells called melanocytes move from deeper in the skin (a layer called the dermis) to the top layer of the skin (the epidermis) by the 20th week of pregnancy. Melanocytes produce melanin, which is the pigment responsible for skin, hair and eye colour.  In congenital dermal melanocytosis, these cells remain in the dermis at birth and continue to produce melanin. The reason for this is unknown. Melanin in the dermis appears blue-grey through the skin, which is why congenital dermal melanocytosis looks like a blue-grey patch on the skin.

Is congenital dermal melanocytosis hereditary?

There may be an underlying inherited cause for this condition, as they are very common in children of Asian, African, Middle Eastern, or Mediterranean descent. 

What does congenital dermal melanocytosis feel and look like?

There are no physical symptoms associated with congenital dermal melanocytosis. The affected areas of skin are not itchy or painful.

Congenital dermal melanocytosis is made of flat, blue-grey, non-raised patches that can appear anywhere on the skin, but most commonly on the lower back and buttocks. The patches occur rarely on the abdomen and limbs, and. Very rarely, on the face and scalp can be affected. It Congenital dermal melanocytosis can be seen as a single patch or multiple patches close together.

Where a very large amount of skin is affected, very rarely this may be associated with inborn errors of metabolism (rare inherited disorders where the body cannot adequately break down food). Your doctor will arrange further tests if they think this could be a possibility.

How is congenital dermal melanocytosis diagnosed? 

Congenital dermal melanocytosis is usually diagnosed by a doctor or midwife, based on its characteristic typical appearance at birth or shortly after. No other diagnostic investigations are required.

Due to the colour and location, they can be mistaken for bruises, which can happen with non-accidental injury. Therefore, it is important that your doctor or midwife record the presence of congenital dermal melanocytosis in the baby and maternal records at initial assessment, to avoid misdiagnosis as bruising at a later date. 

How can congenital dermal melanocytosis be treated? 

Congenital dermal melanocytosis does not require any treatment. The majority fade in childhood and in rare cases, they can persist into adulthood. If the patches do not fade and are causing distress, then options like skin camouflage can be considered. 

Where can I get more information about congenital dermal melanocytosis?

Patient support groups providing information: 

Birthmark Support Group

Tel: 07825 855 888



Changing Faces

Tel: 0300 012 0275



Web links to other relevant sources:

Jargon Buster:

Please note that the BAD provides web links to additional resources to help people access a range of information about their treatment or skin condition. The views expressed in these external resources may not be shared by the BAD or its members. The BAD has no control of and does not endorse the content of external links. 

This leaflet aims to provide accurate information about the subject and is a consensus of the views held by representatives of the British Association of Dermatologists: individual patient circumstances may differ, which might alter both the advice and course of therapy given to you by your doctor. 

This leaflet has been assessed for readability by the British Association of Dermatologists’ Patient Information Lay Review Panel 



Download File