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Pigmented birthmarks

Pigmented birthmarks are usually brown patches on the skin caused by clusters of pigment cells. Examples of pigmented birthmarks include café-au-lait spots, Mongolian spots and congenital melanocytic naevi.

Pigmented birthmarks are different to vascular birthmarks, which are usually red, pink or purple and caused by abnormal blood vessels.

The cause of pigmented birthmarks is not known. However, the amount and location of melanin (a substance that determines skin colour) determines the colour of pigmented birthmarks.

pigmented hairy mole on the child's shoulder

Picture of congenital naevi

Do birthmarks need to be treated?

Most birthmarks need no treatment. They often fade as a child grows older. However, some birthmarks may need treatment because of their location. For example, a raised birthmark near a child's eye may interfere with the ability to see. In rare cases, birthmarks are associated with other conditions, such as growths on the liver, lungs, stomach, or intestines.

Types of pigmented birthmarks

  • Mongolian spots are usually bluish and appear as bruises. They often appear on the buttocks and/or lower back, but they sometimes also appear on the torso or arms. The spots are seen most often in people who have darker skin.
  • Pigmented naevi ( moles) are growths on the skin that are usually flesh-coloured, brown or black. Moles can appear anywhere on the skin, alone or in groups. Moles occur when cells in the skin grow in a cluster instead of being spread throughout the skin. Moles may darken after exposure to the sun, during teenage years and during pregnancy.
  • Congenital naevi are moles that are present at birth. These birthmarks have a slightly increased risk of developing skin cancer depending on their size. Larger congenital naevi have a greater risk of developing skin cancer than do smaller congenital naevi. All congenital naevi should be examined by a doctor and any change in the birthmark should be reported.
  • Cafe-au-lait spots are milky coffee-coloured or light brown spots that are usually oval in shape. They usually appear at birth but may develop in the first few years of a child's life. Cafe-au-lait spots may be a normal type of birthmark, but the presence of several cafe-au-lait spots larger than a 2p coin may occur in neurofibromatosis (a genetic disorder that causes abnormal cell growth of nerve tissues).

What are the symptoms of pigmented birthmarks?

Symptoms of pigmented birthmarks include skin that is abnormally dark or light, or bluish, brown, black or blue-grey in colour. Discolouration of the skin may vary in size and can be smooth, flat, raised or wrinkled. Pigmented birthmarks may increase in size, change colour, become itchy, and may occasionally bleed.

How are pigmented birthmarks diagnosed?

In most cases, doctors can make a diagnosis of birthmarks based on the appearance of the skin. If a mole exhibits potentially cancerous changes, a biopsy may be performed.

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