Medicine in pictures: Epidermal naevi
Epidermal naevi may occur in isolation or be part of a wider syndrome.
Epidermal naevi arise from the basal layer of the embryonic epidermis, which gives rise to skin appendages as well as keratinocytes.
These naevi have been conventionally classified according to the tissue of origin into keratinocytic, sebaceous and follicular types but the use of the general term ‘epidermal naevus' is preferred.
Epidermal naevi can involve any area of skin. They may be present at birth (particularly those on the head) or appear in the first few years of life.
They may simply grow with the patient or can extend well beyond their original distribution over months or years.