A naevus (American spelling nevus, nevi) is a circumscribed and stable malformation of a component of the skin.
Naevi (American spelling nevi) are often present at birth, when they are often called brown birthmarks. Naevicomposed of melanocytes (the pigment cells that produce melanin) are called melanocytic naevi or pigmented naevi.
Naevus of Ota, naevus of Ito and naevus of Hori are special melanocytic naevi that have a slate-brown or blue/grey colouring. They are forms of dermal melanocytosis in which naevus cells are found deep within the dermis.
- Naevus of Ota is on the forehead and face around the eye area. Hyperpigmentation of parts of the eye may occur (sclera, cornea, iris, retina)
- Naevus of Hori is similar to naevus of Ota but affects both sides of the face
- Naevus of Ito is on the shoulder and upper arm area (shoulder girdle)