Ocular melanocytosis (OM) constitutes 6% of all patients diagnosed within the spectrum of oculodermal melanocytosis (ODM), a congenital melanocytic hyperpigmentation of the mucosa! surfaces and facial skin in the distribution of the trigemina! nerve.1 Elevated intraocular pressure with or without glaucoma is the most common complication of ODM and is seen in 10% of the cases.2 The association between open-angle glaucoma and OM is still vague, although the clinical and histopathologic findings of ODM and OM are believed to be identical.1·2 We report a case of a female child with ocular melanocytosis who developed ipsilateral melanocytic glaucoma at very young age that was managed successfully by topical medication.
An 8-year-old girl without any previous ocular problems was found to have elevated intraocular pressure (32 mm Hg) in her right eye while she was examined for pigmented spots on the same eye that were present since birth. Her best-corrected visual acuity was 20/20 in both eyes. The right eye had extensive, patchy, episcleral pigmentation (Fig 1); diffuse inferior corneal endothelial pigment dusting similar to Krukenberg spindle (Fig 2); and marked hyperchromia and thickening of the iris where only the area between the pupillary margin and the collarette was involved. There was no evidence of further involvement of visible dermal and mucosa! surfaces supplied by the trigemina! nerve, and the diagnosis of right OM was made. Gonioscopy revealed a wide open angle with 360° very dense pigmentation partially masking the landmarks. The right choroid was hyperchromic compared with the left eye. The cup-to-disc ratio was 0.5 in the right eye and 0.2 in the left eye. Goldmann perimetry showed generalized depression of the isopters in the right eye. The left eye was entirely normal. She was otherwise healthy and had no family history of glaucoma. She was put on timolol maléate 0.5% twice daily in the affected eye. For the next 7 years, there was no progression of the cupping and visual field changes, and her intraocular pressure remained 16 mm Hg on the average. At no time during the followup was the left intraocular pressure measured above 13 mm Hg.
Fig 1: Patchy episcleral pigmentation of the right eye. There is no dermal involvement.
Several reports have alluded to the association between glaucoma and ODM.1"6 However, only a few have directly addressed the relationship between OM and glaucoma.4,5 Most cases presented in the form of congenital glaucoma, angle-closure or open-angle glaucoma, acute uveitic glaucoma, or ocular hypertension.1·2 In patients with documented open-angle glaucoma, the suspected mechanisms include accumulation of melanocytes in the trabecular meshwork, and differentiation or migration abnormalities of trabecular meshwork cells or melanocytes, both of which are derived from the neural crest.1,2
Weiss and Krohn7 postulated that anterior chamber angle changes alone, in the form of increased outflow resistance caused by excessive amounts of melanocytes, could lead to elevation of the intraocular pressure. On the other hand, in patients with OM and glaucoma, the fellow eyes were found either to have elevated intraocular pressures or be predisposed to open-angle glaucoma, thus implicating other factors rather than simply the melanocytic infiltration.2,4,5 Gonder et al4 found no relation between ipsilateral ocular hypertension and OM and the degree of pigmentation.
Some authors5 believe that the association between OM and secondary open-angle glaucoma would be relatively infrequent as a "double hit" in the form of an already poor reserve of aqueous outflow followed by melanocytic infiltration would be necessary before glaucoma could develop.
Interestingly, of the three patients with ODM and glaucoma diagnosed before age 10 that were reported in the literature, two had associated Klippel-Trenaunay-Weber syndrome, and one had late-onset congenital glaucoma.2 Our patient did not have any associated disease, and in contrast to the other reported cases (except for a patient described by Teekhasaenee et al2), the fellow eye remained normal.
Fig 2: Magnified view of the right inferior cornea showing endotkelial pigment granules similar to Krukenberg spindle. More recent deposits have dendritic margins and appear darker than the more chronic ones.
Corneal endothelial pigment dusting is a relatively rare finding and has been noted in 12% of patients with ODM.1 Krukenberg-type pigment dusting was present in only two out of 20 patients with ODM and glaucoma.2 In ODM, corneal pigmentation may also result from migration of melanocytes from the conjunctiva to the corneal epithelium or stroma or from misdirected melanocytes during embryogenesis.8 The significance of endothelial pigment dusting in ODM in association with glaucoma remains unknown.
Our patient demonstrates that OM may be associated with open-angle melanocytic glaucoma early in life so that these patients should be closely monitored not only for possible neoplastic, but for elevated intraocular pressures as well, even in childhood.
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