Sir,

Oculodermal melanosis (ODM) or Nevus of Ota is a congenital condition characterized by benign dermal melanosis of the skin in the area innervated by first, second, and rarely third division of the trigeminal nerve. Patients develop ipsilateral increase in pigmentation of the episclera, conjunctiva, uveal tract, and occasionally optic nerve head. In Caucasians, there is an association between ODM and uveal melanoma.1, 2 The disease, on the other hand, is rare in blacks. We report here a case of ODM and uveal melanoma in a black patient.

Case report

A 46-year-old Kuwaiti black female presented with a blind painful left eye of 1 year-duration. Patient is a known case of ODM involving the left side of her face. She had no light perception with intractable glaucoma despite full medical treatment. The right eye showed normal findings. The left eye revealed diffuse scleral pigmentation, corneal oedema, rubeosis iridis, and subtotal posterior synechiae (Figure 1a). The fundus could not be viewed because of vitreous haemorrhage. B-scan ultrasonography revealed a large choroidal mass in the posterior pole with total retinal detachment and vitreous opacities (Figure 1b). A-scan revealed high internal reflectivity of the mass suggestive of melanoma. Work-up for systemic metastasis was negative. Magnetic resonance imaging of the brain and abdomen, and liver function tests were normal. Patient underwent modified enucleation and sphere implantation; the procedure involved enucleation with excision of the surrounding fat. Pathology report confirmed the diagnosis of malignant choroidal melanoma of the epithelioid type with free optic nerve surgical margin and no signs of vascular invasion (Figure 1c). Patient had a smooth postoperative course. Follow-up at 1 year postoperatively revealed no local or systemic metastasis.

Figure 1
figure 1

(a) Left eye scleral pigmentation. (b) B scan of left globe showing large mushroom choroidal elevation with retinal detachment. (c) The epithelioid melanoma cells showing large nuclei with prominent nucleoli (haematoxylin–eosin × 160).

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Comment

In Caucasians, an association between ODM and uveal melanoma is well recognized. It is estimated that one in 400 patients with ODM followed for life develop uveal melanoma, as compared to one of 13 000 in the general population.3 There are, however, only a few cases of such association in black patients reported in the literature.4, 5, 6, 7, 8, 9 This might be due to under-reporting or a true negative association. It is believed that the higher prevalence of melanomas in fair skin patients is attributed to the lack of the protective effect of darker pigmentation.10 However, this protective effect must be incomplete to explain the occurrence, although to a lesser extent, of melanoma in association with ODM in dark patients. Melanin is a photoreactive compound and can paradoxically act as a photosensitizer, as well as a photoprotector. Most darkly pigmented individuals had significantly heavier choroidal pigmentation than white patients in this study. Dark pigmented patients produce eumelanin, which has greater protective effects than pheomelanin, more commonly produced in fair-skinned individuals.10 Therefore, a balance between the types of melanin, its density, and distribution would explain the balance between its photosensitizer and photoprotector effect.

To our knowledge, our case is the first in Eastern Mediterranean countries of a black patient with ODM and uveal melanoma. Although there are too few cases of this association to draw conclusions, we believe that even black individuals with ODM are at some risk of developing uveal melanoma. Therefore, we suggest that all patients with ODM, regardless of their race, should have periodic ocular examination to allow early detection of uveal melanoma.