naevus

n. (pl. naevi)

a birthmark: a clearly defined malformation of the skin, present at birth. There are many different types of naevi. Some, including the strawberry naevus and port-wine stain, are composed of small blood vessels (see haemangioma). The strawberry naevus (or strawberry mark) is a raised red lump usually appearing on the face and growing rapidly in the first month of life. These birthmarks slowly resolve and spontaneously disappear between the ages of five and ten. The port-wine stain (or capillary naevus) is a permanent purplish discoloration that may occur anywhere but usually appears on the upper half of the body. Laser treatment can reduce the discoloration. Occasionally a port-wine stain may be associated with a malformation of blood vessels over the brain, for example in the Sturge-Weber syndrome (see angioma).

It is not uncommon for a pale or white halo to develop around an ordinary pigmented naevus, especially on the trunk, forming a halo naevus. The pigmented naevus disappears over the course of a few months; this is followed by resolution of the pale area. A blue naevus is a small blue-grey papule appearing at birth or later in life, mainly on the extremities. Progression to malignant melanoma is very rare. A naevus of Ota is a blue-grey pigmented area on the cheek, eyelid, or forehead with similar pigmentation of the sclera of an eye. It is associated with melanomas of the uvea, orbit, and brain as well as with glaucoma of the affected eye. See also mole.