Naevus of Ota and Naevus of Ito
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Direct answer
Naevus of Ota is a blue-grey dermal melanocytosis that follows the ophthalmic and maxillary divisions of the trigeminal nerve, and naevus of Ito is the same process over the posterior shoulder and upper arm. The melanocytes lie deep in the dermis, and their pigment appears blue through light scatter. Q-switched lasers treat both effectively, but the eye must be examined in naevus of Ota because ocular melanocytosis is common.
What you must remember
- Dermal melanocytosis: melanocytes sit deep in the dermis, and the blue or slate colour results from light scattering, the Tyndall effect.
- Naevus of Ota: unilateral, over the V1 and V2 territories, with periocular and malar involvement.
- Naevus of Ito: over the posterior shoulder, supraclavicular area and upper arm, and usually spares the eye.
- Ocular involvement: scleral and uveal melanocytosis occur with naevus of Ota, raising the risk of glaucoma and uveal melanoma.
- Onset: the lesion is often present from birth or childhood, may darken at puberty, and acquired forms in adult women are described.
- Epidemiology: commonly reported in Asian and darker-skinned populations, with a female predominance.
- Laser treatment: Q-switched lasers, including the Nd:YAG and alexandrite types, are used over several sessions, with the Nd:YAG preferred in darker skin.
- Complications: post-laser hypopigmentation and incomplete clearance are the main concerns, so counselling is essential.
Assessing and treating facial dermal melanocytosis
A 14-year-old girl has a slate-blue patch over the left cheek and forehead, with blue discolouration of the sclera on the same side. The steps below structure her assessment and treatment.
- Define the distribution: Map the patch to the trigeminal divisions V1 and V2 for naevus of Ota, or to the posterior shoulder and upper arm for naevus of Ito.
- Examine the eye: Inspect the sclera, conjunctiva and iris, and refer for ophthalmic review to detect uveal melanocytosis and glaucoma.
- Confirm the diagnosis: Clinical features are usually enough, and a biopsy is reserved for atypical or changing lesions, which show dendritic melanocytes in the dermis.
- Record a baseline: Photograph the lesion and document its size and depth of colour, so that response to treatment can be compared over time.
- Choose a laser: Q-switched lasers are used at settings suited to skin type, and the Nd:YAG laser is generally preferred in darker skin.
- Plan sessions and counsel: Expect several sessions, a risk of post-laser hypopigmentation, and partial improvement in many patients.
Where the exam tries to catch you
Naevus of Ota questions test the ocular link, the distribution and the logic of the laser choice.
- Trap: calling naevus of Ota a harmless naevus that needs no ocular review. Correct: ocular melanocytosis can cause glaucoma and carries a risk of uveal melanoma, so eye assessment is mandatory.
- Trap: attributing the blue colour to pigment in the epidermis. Correct: the colour arises from deeply placed dermal melanocytes that scatter light, a principle that also explains the Mongolian spot.
- Trap: labelling a shoulder lesion as naevus of Ota. Correct: naevus of Ota follows the trigeminal face, whereas naevus of Ito lies over the shoulder and upper arm, so the distribution determines the label.
Frequently asked questions
Which nerve divisions are involved in naevus of Ota?
Naevus of Ota most often involves the ophthalmic (V1) and maxillary (V2) divisions of the trigeminal nerve, and the lesion is usually unilateral. Involvement of the mandibular division (V3) is less common than involvement of the upper divisions.
What is the main ocular concern in naevus of Ota?
Naevus of Ota can cause ocular melanocytosis of the sclera and uvea, which raises the risk of glaucoma and uveal melanoma. Ophthalmic examination is therefore part of the assessment, even when the skin lesion looks minor.
Why are Q-switched lasers used to treat naevus of Ota?
Q-switched lasers deliver very short pulses that selectively target melanin in dermal melanocytes while sparing surrounding tissue. Several sessions are needed, and the Nd:YAG laser is preferred in darker skin because it is less absorbed by epidermal melanin.
How does naevus of Ito differ from naevus of Ota?
Naevus of Ito lies over the posterior shoulder, supraclavicular area and upper arm, whereas naevus of Ota lies on the face in the trigeminal distribution. Naevus of Ito usually does not involve the eye, which is the key clinical difference between the two.