Combined hamartoma of retina and retinal pigment epithelium

Description

A hamartoma is a benign congenital tissue malformation made up of cells in their normal location but that are malformed or misarranged. A combined hamartoma of the retina and retinal pigment epithelium (RPE), similar to a congenital hypertrophy of the RPE (CHRPE), has RPE cells that are larger and contain more melanin pigment granules than normal. In addition, the combined hamartoma also has characteristics of an astrocytic hamartoma, with abnormal astrocytes in the nerve fibre layer or optic nerve.
There is distortion and tortuosity of the involved vasculature, and in some cases the lesion may also originate partly from the vasculature. The lesions share normal ocular growth patterns and are neither malignant nor metastasizing. Although the principal challenge for the clinician is to differentiate such pigmented lesions from a malignant melanoma, secondary nonmalignant complications are also possible.

Symptoms

A combined hamartoma of the retina and RPE often does not cause symptoms. If the lesion is adjacent to the fovea,there may be a gradual blurring of vision as a result of secondary changes in the vitreoretinal interface followed by retinal traction. It is usually unilateral.

Signs

Combined hamartoma of the retina and RPE is typically pigmented grey with white areas. It may appear as a raised or fullW thickness retinal lesion, with vascular tortuosity, and usually with surface fibrosis and vitreoretinal interface changes. The latter changes may be seen on ophthalmoscopic examination as similar to an epiretinal membrane or surface wrinkling retinopathy. Combined hamartoma of the retina and RPE may be an isolated retinal finding or may partly overlie the optic nerve head. Surrounding tissue and retinal blood vessels appear normal and the overlying vitreous is clear. Secondary complications may occur. The epiretinal membrane may distort the macula or lead to other signs of retinal stress including holes. If the vasculature is incompetent, there may be lipid exudate or subretinal fluid accumulation causing serous macular detachment. Choroidal neovascularization and vitreous hemorrhage are other rare complications. Systemic associations have been occasionally reported.

Prevalence

Uncommon (approximately 1/1,000) to rare (approximately 1/10,000)

Significance

Benign with usually a low threat to sight from secondary changes.

Differential diagnosis

Melanoma – malignant; congenital hypertrophy of the RPE; choroidal nevus, melanocytoma of the optic nerve, retinoblastoma, choroidal neovascularization or hemorrhage.

Management

Additional Investigations A combined hamartoma of the retina and RPE can usually be diagnosed from its characteristic ophthalmoscopic appearance. Iffluorescein angiography is required, it will show early hypofluorescence, caused by blocking of the choroidal glow by RPE proliferation, although there will be gradual leakage of fluorescein from the tortuous vessels within the lesion.

Incisional surgery If retinal traction causes significant visual loss, then a vitrectomy and removal of the epiretinal membrane may be indicated. Surgery is intended to stabilize vision and prevent further loss.

Review As lesions are usually not progressive, regular review, perhaps on an annual basis, is often the only management required. Fundus photography or ultrasonography may be used to monitor the lesion for growth or change. If retinal traction causes visual loss, then surgical management may be indicated.