Naevus of Ota

Naevus of Ota (oculodermal melanocytosis) is a congenital or early onset blue grey to brown patch of dermal melanocytosis in the area supplied by the first and second divisions of the trigeminal nerve. It often involves the sclera, uvea and other ocular tissues on the same side.

It is commonest in people of Asian descent (about 0.2 to 0.6%) and in Black people, and is much rarer in White people. Women are affected about four times as often as men. About half of cases are present at birth and most of the rest appear in adolescence.

The cutaneous lesion is benign. The main risks are secondary glaucoma (about 10%) and, rarely, uveal or orbital melanoma, which is reported mainly in White patients.

Pathophysiology.

Mosaic activating variants in GNAQ or GNA11 cause dermal melanocytes that failed to complete migration from the neural crest to the epidermis to persist in the dermis. Their pigment, seen through the skin, gives the blue grey colour (Tyndall effect).

Hormonal change at puberty and sun exposure can darken lesions.

• Unilateral (5% bilateral) speckled or confluent blue grey patch on the forehead, temple, cheek, periorbital skin and nose, sometimes with scleral and conjunctival pigmentation.
• Pigment can also involve the oral mucosa, tympanic membrane, nasal mucosa and the pigment layer of the iris and choroid.
• Slow darkening and extension with age. Spontaneous resolution does not occur.

Red flags.

• Eye pain, blurred vision, halos or raised intraocular pressure (glaucoma).
• Growing or changing pigmented lesion in the eye, or new visual field loss (uveal melanoma).
• Rapidly enlarging nodule within the patch (cutaneous melanoma, blue naevus like change).

• Clinical diagnosis from pattern, distribution and onset. Dermoscopy shows structureless blue grey to brown areas.
• Biopsy is needed only if a nodule appears or the diagnosis is uncertain: elongated dendritic melanocytes scattered in the upper and mid dermis.
• Ophthalmology at diagnosis with slit lamp examination, intraocular pressure and dilated fundus examination.

Differential diagnosis.

• Hori naevus (acquired bilateral naevus of Ota like macules, onset in adulthood), melasma and lichen planus pigmentosus.
• Mongolian spot, blue naevus, and café-au-lait macules in infants.
• Ochronosis, argyria, drug induced pigmentation (minocycline, amiodarone) and port wine stain in a very young child.

• Explain that the lesion is benign and persistent, and that treatment is for appearance.
• Q-switched lasers (ruby 694 nm, alexandrite 755 nm or neodymium doped yttrium aluminium garnet 1064 nm), or picosecond lasers, are first line. Expect 4 to 10 sessions at intervals of 3 months, with good clearance in most patients. Treating in childhood needs fewer sessions.
• Post-inflammatory hyperpigmentation is the commonest adverse effect, especially in darker skin, and scarring and hypopigmentation are less common. Use sunscreen of at least SPF 30 and avoid sun exposure before and after sessions.
• Camouflage cosmetics where laser is not wanted or between sessions.
• Eye review every year (intraocular pressure and fundus examination) for life.
• Glaucoma needs treatment by ophthalmology. Uveal or cutaneous melanoma is managed by an oncology team.

Special groups. Fair skinned patients (higher melanoma risk) need ophthalmology review every 6 months.

Monitoring. Skin check yearly for new nodules, ophthalmology yearly.

Referral and escalation. Ophthalmology for every patient at diagnosis; dermatology for laser; urgent referral for a new nodule or visual change.