Shahmeer Hamid
Introduction
Oculodermal melanocytosis, classically known as Nevus of Ota, is a congenital or acquired pigmentary disorder characterised by blue-grey hyperpigmentation of the skin and mucous membranes in the distribution of the ophthalmic (V1) and maxillary (V2) divisions of the trigeminal nerve. It was first described in 1939 by Dr. M. Ota. The condition arises from the incomplete migration of melanocytes from the neural crest to the epidermis during embryonic development, leading to their entrapment within the dermis and ocular tissues (1).
It predominantly affects Asian and African populations, with a female-to-male ratio of approximately 5:1. While most cases are unilateral (90-95%), bilateral involvement occurs in about 5-10% of patients and is associated with a slightly earlier age of onset (2).
Clinical Stages and Classification
Nevus of Ota is often classified based on the extent of dermal involvement (Tanino Classification), though clinically, it is defined by its specific ocular and cutaneous features:
Cutaneous Features
Pigmentation
Irregular, patchy, or confluent macules ranging from slate-grey to brown or blue-black.
Distribution
Strictly follows the V1 (forehead, eyelid) and V2 (cheek, temple) trigeminal dermatomes.
Onset
Bimodal onset; roughly 50% present at birth (congenital), with a second peak occurring during puberty due to hormonal influences (3).
Ocular Features
Sclera
The most common ocular sign is slate-blue or grey pigmentation of the episclera and sclera.
Iris
Heterochromia is common, with the affected iris appearing darker (hyperchromic). Mammillations (small, velvety elevations on the iris surface) may be present.
Fundus
The fundus often exhibits a “dark choroid” appearance due to increased choroidal pigmentation, darker than the fellow eye.
Investigations
Diagnosis is primarily clinical, but specific evaluations are critical to monitor for complications.
Slit-Lamp Examination
To assess iris mammillations and scleral pigmentation.
Gonioscopy
Essential for detecting hyperpigmentation of the trabecular meshwork, which correlates with glaucoma risk.
Dilated Fundus Exam
To screen for choroidal nevus or early signs of uveal melanoma.
Ultrasound Biomicroscopy (UBM) / Anterior Segment OCT
Can visualize ciliary body cysts or widening, which may indicate early glaucoma risk mechanisms.
Dermatology Referral
For assessment of cutaneous lesions, although biopsy is rarely needed unless malignant transformation is suspected.
Differential Diagnosis
Conditions to differentiate from Nevus of Ota include:
Nevus of Ito
Similar dermal melanocytosis but involves the distribution of the posterior supraclavicular and lateral cutaneous brachial nerves (shoulder/upper arm area).
Hori’s Nevus (Acquired Bilateral Nevus of Ota-like Macules)
Bilateral, acquired in adulthood, and typically lacks mucosal or ocular involvement.
Congenital Dermal Melanocytosis (Mongolian Spot)
Typically located on the lumbosacral area and usually resolves during childhood (4).
Ocular Melanoma
Must be ruled out if a new, elevated, or changing pigmented lesion appears.
Drug-Induced Hyperpigmentation
Can mimic cutaneous findings (e.g., minocycline, amiodarone).
Management
Management requires a multidisciplinary approach focusing on cosmetic concerns and surveillance for vision-threatening complications:
Dermatological (Cosmetic)
Q-switched lasers (e.g., Nd:YAG, Ruby, or Alexandrite) are the gold standard for treating cutaneous pigmentation, offering high success rates with low risk of scarring (5).
Ophthalmological (Surveillance)
Glaucoma
Life-long annual or bi-annual monitoring of intraocular pressure (IOP) is mandatory. Medical therapy (prostaglandin analogues, beta-blockers) is the first line, though surgery (trabeculectomy/tube shunt) may be required for refractory cases.
Melanoma
Periodic dilated fundus exams are critical to detect choroidal melanoma early (2).
Prognosis
The cosmetic prognosis is excellent with modern laser therapy. However, the ocular prognosis depends on the development of complications:
Glaucoma
Approximately 10% of patients develop elevated IOP or glaucoma in the affected eye due to melanocytic obstruction of the trabecular meshwork.
Malignancy
There is an estimated 1 in 400 lifetime risk of developing uveal melanoma (choroidal, ciliary body, or iris), which is significantly higher than the general population. Cutaneous melanoma arising within the nevus is rare but reported.
Neurological
Rarely, extensive meningeal melanocytosis can occur, potentially leading to CNS complications, though this is exceptionally uncommon (6).
Conclusion
Oculodermal melanocytosis (Nevus of Ota) is a distinct congenital dyschromia affecting the skin and eye along the trigeminal nerve distribution. While the cutaneous manifestations are benign and treatable, the condition carries significant lifelong risks for ocular glaucoma and uveal melanoma. Therefore, patients require lifelong ophthalmologic surveillance to prevent irreversible vision loss and detect potential malignancies early.
References
1. Ota M. Nevus fusco-caeruleus ophthalmo maxillaris. Tokyo Med J. 1939;63:1243–1245.
2. Shields JA, Shields CL, Scartozzi R. Survey of 1264 patients with orbital tumors and simulating lesions: The 2002 Montgomery Lecture, part 1. Ophthalmology. 2004;111(5):997-1008. doi:10.1016/j.ophtha.2003.01.002
3. Teekhasaenee C, Ritch R, Rutnin U, Leelawongs N. Glaucoma in oculodermal melanocytosis. Ophthalmology. 1990;97(5):562-570. doi:10.1016/s0161-6420(90)32540-x
4. Lapeere H, Boone B, De Schepper S, Verhaeghe E, Van Geel M, Ongenae K, Van Geel N, Lambert J, Brochez L. Chapter 75. Hypomelanoses and Hypermelanoses. In: Goldsmith LA, Katz SI, Gilchrest BA, Paller AS, Leffell DJ, Wolff K. eds. Fitzpatrick’s Dermatology in General Medicine, 8e. The McGraw-Hill Companies; 2012. https://accessmedicine.mhmedical.com/content.aspx?bookid=392§ionid=41138777
5. Chan HH, Kono T. Nevus of Ota: clinical aspects and management. Skinmed. 2003;2(2):89-98. doi:10.1111/j.1540-9740.2003.01706.x
6. Patel BC, Egan CA, Lucius RW, Gerwels JW, Mamalis N, Anderson RL. Cutaneous malignant melanoma and oculodermal melanocytosis (nevus of Ota): report of a case and review of the literature. J Am Acad Dermatol. 1998;38(5 Pt 2):862-865. doi:10.1016/s0190-9622(98)70477-3