Congenital choroidal melanocytoma in a child with ocular melanocytosis

Disrupting Hedgehog signaling in melanocytes by SUFU knockout leads to ocular melanocytosis and anterior segment malformation

Hedgehog (Hh) signaling is well known for its crucial role during development, but its specific role in individual cell lineages is less well characterized. Here, we disrupted Hh signaling specifically in melanocytes by using Cre-mediated cell-type-specific knockout of the Hh regulator suppressor of fused (Sufu). Interestingly, corresponding mice were fully pigmented and showed no developmental alterations in melanocyte numbers or distribution in skin and hair follicles. However, there were ectopic melanoblasts visible in the anterior chamber of the eye that eventually displayed severe malformation. Choroidal melanocytes remained unaltered. Surprisingly, the abnormal accumulation of anterior uveal melanoblasts was not the result of increased cell proliferation but of increased migration to ectopic locations such as the cornea. In melanoblasts in vitro, Sufu knockdown replicated the increase in cell migration without affecting proliferation and was mediated by an increased level of phosphorylated-ERK brought about by a reduction in the levels of the repressor form of GLI3. These results highlight the developmental divergence of distinct melanocyte subpopulations and may shed light on the pathogenesis of human ocular melanocytosis.

A case of choroidal melanocytosis observed by multimodal imaging with laser speckle flowgraphy

BACKGROUND

Choroidal melanocytosis is characterized by congenital diffuse melanin pigmentation with extensive parenchymal infiltration of spindle cells in the choroid; however, little is known about the choroidal circulation and morphological changes. We herein report a case of choroidal melanocytosis observed by multimodal imaging with laser speckle flowgraphy (LSFG).

CASE PRESENTATION

A 56-year-old woman was referred to our hospital because of serous retinal detachment (SRD) in her left eye. At the initial examination, her best-corrected visual acuity (BCVA) was 1.5 oculus dexter (OD) and 0.8 oculus sinister (OS). An irregular, flat, brownish lesion was noted around the macula OS. Optical coherence tomography showed a choroidal structure with marked hyporeflectivity and SRD where the retinal thickness was preserved. Indocyanine green angiography demonstrated fluorescence blockade throughout. Fundus autofluorescence revealed enlarged macular hypofluorescence, suggesting chronic retinal pigment epithelium damage associated with prolonged SRD. B-mode echography showed no choroidal elevation. Based on the clinical findings, the left eye was diagnosed with choroidal melanocytosis. Four years and 10 months after the initial visit, her BCVA was 0.5 and SRD remained. During the entire period of observation, the mean blur rate (MBR) (mean ± standard deviation) of choroidal blood flow velocity on LSFG was 10.15 ± 0.72 arbitrary units (AU) OD and 1.31 ± 0.06 AU OS.

CONCLUSION

Choroidal melanocytosis presented with chronic minor circulatory disturbances due to melanocyte proliferation in the choroid, but the markedly low MBR values by LSFG were dissociated from her retinal thickness and visual function. The proliferation of melanocytes may be a cause of overestimating the cold-color signal of LSFG due to their pigmentation.

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.