Isolated choroidal melanocytosis: clinical update on 37 cases.

Purpose: Isolated choroidal melanocytosis is a congenital melanocytic hyperpigmentation involving the choroid that is not associated with iridic or scleral features of ocular melanocytosis. The purpose of this work was to describe the clinical features and course of a relatively large series of patients with this disorder.

Methods: A retrospective clinical study of 37 patients with isolated choroidal melanocytosis encountered in a single practice 1986-2018 was done. All lesions were 5 mm or larger in the largest basal diameter, homogeneously melanotic, and completely flat by conventional ocular ultrasonography.

Results: The 37 patients ranged in age from 2 weeks to 87 years (mean 31.5 years, median 18 years) at initial diagnosis of the melanotic choroidal lesion. Arc length largest basal diameter of the melanotic choroidal lesion ranged from 5.5 to 37 mm (mean 14.6 mm, median 13 mm). The lesion extended beneath the fovea in 18 eyes and to the optic disc margin in 6 eyes. Ten of the lesions straddled the ocular equator, but the center point of all of the lesions was posterior to the equator. The retina was fully attached and appeared normal over the melanotic choroidal lesion in each of these eyes. None of the melanotic choroidal lesions exhibited clumps of orange pigment or drusen on its surface. The lesion was unilateral and unifocal in 36 of the 37 patients. One patient had bilateral choroidal melanocytosis that was isolated in one eye but associated with partial iris melanocytosis in the fellow eye. Three adult patients had a choroidal melanoma localized to the patch of choroidal melanocytosis at baseline. One other adult patient had a choroidal melanoma in the fellow eye at baseline. One pediatric patient had viable unilateral non-familial retinoblastoma in the fellow eye and two adult patients had a classic choroidal nevus in the fellow eye. None of the flat patches of choroidal melanocytosis that were monitored periodically after initial diagnosis expanded appreciably during follow-up ranging from 4.9 months to 15.2 years (mean 5.0 years, median 2.3 years).

Conclusions: Isolated choroidal melanocytosis is a distinct clinical entity that must be distinguished from broad-based choroidal nevus, choroidal melanocytoma, small choroidal malignant melanoma, acquired bilateral patchy-streaky choroidal melanocytic fundopathy associated with disorders such as cutaneous vitiligo and Waardenburg syndrome, acquired bilateral zonal choroidal melanocytic fundopathy, and diffuse uveal melanocytic proliferation associated with systemic cancer. This disorder appears to predispose affected eyes to development of choroidal melanoma arising from the hypermelanotic patch.