Naevi of Ota and Ito
What are naevi of Ota, Ito and Hori?
A naevus (plural naevi, American spelling nevus, nevi) is a circumscribed and stable malformation of a component of the skin. Naevi are often present at birth, when they are often called birthmarks. Naevi composed of the pigment cells that produce melanin (melanocytes) are called melanocytic naevi.
Naevus of Ota, naevus of Ito and naevus of Hori are melanocytic naevi with slate-brown or blue/grey colouring. The naevus cells are found deep within the dermis, a form of dermal melanocytosis.
- 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 is on both sides of the face
- Naevus of Ito is on the shoulder and upper arm area (shoulder girdle).
Dermal melanocytosis can also occur elsewhere on the body, including inside the mouth.
How does dermal melanocytosis arise, and who is at risk?
It is not known why dermal melanocytosis occurs. Specific mutations have been detected within the dermal melanocytes, most often GNAQ or GNA11. Researchers have suggested that hormones play a part in their development. The role of ultraviolet radiation is thought to be small, as it does not reach deep dermal melanocytes.
Naevus of Ota is much more common than naevus of Ito. These naevi are present at birth in 50% of cases but may appear during adolescence or adult life. Naevus of Hori is not present at birth and is therefore a form of acquired melanocytosis.
Naevi of Ota and Ito are most commonly found in Asian populations; 0.2-0.6% of Japanese people have nevi of Ota. They appear more frequently in females. Both forms of naevi are uncommon in Caucasians.
What are the signs, symptoms and complications of dermal melanocytosis?
In all forms of dermal melanocytosis:
- Colour may vary to include brown-violet, violet-blue or blue-green hues
- Naevi present in childhood may slowly grow and darken until adulthood is reached
- Colour or perceived colour of naevi may change according to personal and environmental conditions, e.g. fatigue, menstruation, hot weather
- If affecting the eye, melanocytosis rarely causes glaucoma
- Malignant melanoma very rarely develops within dermal melanocytosis, and has usually been reported in Caucasians. Ocular melanoma has been reported in the choroid, brain, orbit, iris, ciliary body, and optic nerve in association with a nevus of Ota.
How is the diagnosis of dermal melanocytosis made?
The diagnosis of dermal melanocytosis is usually made by observing typical discolouration of the skin. It is classified according to the site affected.
Some patients may undergo skin biopsy, which confirms the presence of melanocytes in the dermis.
Other skin conditions resulting in bluish or grey coloured skin may be considered. These include:
- Blue naevus
- Drug-induced pigmentation, eg due to minocycline, a tetracycline antibiotic
- Postinflammatory pigmentation
- Lichen planus pigmentosus and ashy dermatosis
What treatments are available for melanocytosis?
Treatment of a melanocytosis includes:
- Cosmetic camouflage to cover the disfiguring markings.
- Laser treatment (usually using 1064nm Q switched Nd:YAG or QS ruby laser) and intense pulsed light (IPL). These work by destroying the dermal melanocytes. Multiple treatments are necessary, often with a combination of devices. Laser treatment is more effective in light skinned individuals than in those with dark skin. Unfortunately recurrence is common after laser clearance, sometimes resulting in a darker hue.
If the eye is affected, regular eye examinations should be arranged to detect glaucoma. Any change in a naevus should be assessed by a dermatologist.