Dermatology MCQ - Infiltrative and Neoplastic Disorders - Naevus of Ota

A 25-year-old woman of Asian descent presents for consultation regarding a bluish-brown discoloration of the skin around her right eye that she has had since adolescence. On examination, there is a mottled, hyperpigmented patch involving the right periorbital skin, the temporal region, and the sclera of the ipsilateral eye. The lesion is flat and has not changed in recent years. What is the most significant long-term risk associated with this condition?

A. Progressive transformation into a large, congenital melanocytic nevus with potential for malignant degeneration.
B. An increased risk of developing open-angle glaucoma in the affected eye.
C. Spontaneous, complete resolution of the cutaneous pigmentation by the fifth decade of life.
D. The development of Sturge-Weber syndrome, with associated leptomeningeal and ocular vascular anomalies.
E. A high likelihood of systemic metastasis from the dermal melanocytes.

Correct Answer: B. An increased risk of developing open-angle glaucoma in the affected eye.

Answer and Explanation

The correct answer is B. This question describes the classic presentation of Naevus of Ota (or Oculodermal Melanocytosis). The key clinical clues are the unilateral distribution along the ophthalmic and maxillary divisions of the trigeminal nerve, the bluish-brown color, the scleral involvement, and the onset in childhood or adolescence.

The most significant long-term medical risk is ipsilateral open-angle glaucoma, which occurs in approximately 10% of patients. The melanocytes can also involve the iris (leading to heterochromia) and the fundus, increasing intraocular pressure.

Why the Other Options are Incorrect:

• A. Progressive transformation into a large, congenital melanocytic nevus...: This is incorrect. A Naevus of Ota is a distinct form of dermal melanocytosis. It does not transform into a different type of nevus. While there is a small risk of malignancy (see below), it is not a precursor to a congenital melanocytic nevus.

• C. Spontaneous, complete resolution of the cutaneous pigmentation...: This is incorrect. Unlike Mongolian spots, Naevus of Ota is almost always persistent and stable throughout life. It does not resolve spontaneously.

• D. The development of Sturge-Weber syndrome...: This is incorrect. Sturge-Weber syndrome is a neurocutaneous disorder characterized by a port-wine stain (a capillary vascular malformation) in the trigeminal distribution, not a dermal melanocytosis. It is associated with leptomeningeal angiomas and seizures, not glaucoma.

• E. A high likelihood of systemic metastasis...: This is incorrect and overly alarmist. The melanocytes in Naevus of Ota are benign. However, there is a slightly increased risk of malignant transformation within the lesion, potentially leading to melanoma (primarily ocular or cutaneous). The lifetime risk is estimated to be low (around 1-2%), but it is not zero. This risk is significant, but the most common and well-established long-term risk is glaucoma, making B the best answer.

Additional High-Yield Information for Exams:

• Histopathology: Identical to a Mongolian spot, showing dendritic melanocytes scattered in the upper and mid-dermis. The key difference from a Mongolian spot is the anatomical location and its persistence.

• Differential Diagnosis:

  • Mongolian Spot: Located on lumbosacral area, typically resolves.

  • Naevus of Ito: Same histology, but located in the supraclavicular, scapular, and deltoid regions (acromioclavicular distribution).

  • Acquired Bilateral Nevus of Ota-like Macules (Hori's Nevus): Appears in adulthood, is often bilateral, and typically spares the sclera and mucosa.

  • Ecchymosis/Bruising: Will resolve and change color.

• Associated Conditions & Prognosis:

  • Ocular Complications: As stated, glaucoma is the most common and serious association. Involvement of the conjunctiva, iris, and fundus is also possible.

  • Malignancy Risk: There is a small but real increased risk of melanoma developing within the lesion, either in the skin or, more commonly, within the uveal tract of the eye. This necessitates regular ophthalmologic surveillance.

• Management & Rationale:

  • Rationale: Management focuses on screening for and managing complications, not necessarily treating the cosmetic appearance unless desired.

  • First-line/Obligatory: Referral to an ophthalmologist for a comprehensive baseline examination and periodic monitoring for glaucoma and ocular melanoma.

  • Cosmetic Treatment: If desired for cosmetic reasons, Q-switched lasers (e.g., Nd:YAG, Alexandrite) are the treatment of choice and can significantly lighten the pigmentation.

  • Surveillance: Patients should be educated about the signs of melanoma and the importance of regular skin and eye exams.