Congenital nevi

What are they naevi?

Congenital Nevi or birthmarks are essentially colored skin marks that develop before or shortly after birth. Naevi are sometimes called hamartomasthey are messy proliferations of cells within the tissue of origin, and are due to developmental error.

Benign Developmental skin lesions that develop later in life are called "acquired" nevi.

Naevi can be derived from the outer layers of the skin (epithelial naevi) or from the deeper layers (dermal/ /subcutaneous naevi). Naevi are further classified according to the type of cell involved. Melanocytic and vascular Nevi are generally the most common types of birthmarks.

What causes nevus?

Nevi are caused by visible clusters of cells on the skin. Vascular nevi are due to groups of blood vessels, melanocytic nevi are due to groups of pigmented skin cells (melanocytes), epidermal nevi to keratinocytes skin cells and so on. The exact cause of why they occur is unknown, but may be related to located anomalies of certain genes. There is no known way to prevent them.

New ideas related to mosaicism (the phenomenon of two cell lines arising early in embryonic development) are being explored, as many congenital nevi have been observed to follow Blaschko's lines.

What treatment is available?

See individual birthmark types for specific treatment options.