Congenital hypertrophy of the retinal pigment epithelium

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) lesions are pigmented lesions of the retinal pigment epithelium (RPE) that are flat or very slightly raised, round or oval, and predominantly located at the mid-periphery as well as in the peripapillary or macular regions (Fig. 47.1). A pigmented and non-pigmented halo may surround lesions with multiple depigmented lacunae within the lesion. Depigmented CHRPEs are less common.¹ Optical coherence tomography (OCT) demonstrates lack of photoreceptors overlying the lesion² while absent autofluorescence shows a lack of lipofuscin. Fluorescein angiography demonstrates choroidal masking.³

Fig. 47.1 Congenital hypertrophy of the retinal pigment epithelium (CHRPE). Slightly raised jet black lesion in the mid-periphery with an associated small visual field defect.

(Professor A. C. Bird’s patient.)

Associations

Vascular sheathing, vessel attenuation and microangiopathy, drusen, adjacent white-without-pressure, and adjacent depigmented linear RPE streaks are found on or around lesions. Lesions gradually enlarge in diameter; 83% of lesions enlarged at a rate of 2 µm/mm lesion-base per month.¹ Flat CHRPE are rarely associated with visual loss. A small proportion (1.5%) contain nodules. Visual loss may occur due to macular edema. Exceptionally, malignant transformation occurs within nodular lesions.⁵

CHRPE associated with adenomatosis polyposis of the colon

The majority of CHRPEs have neither visual nor health implications. However, multiple (more than three), bilateral, mixed pigmented, and depigmented CHRPEs are specific and sensitive markers of adenomatous polyposis of the colon (APC), or familial adenomatous polyposis (FAP). In APC, CHRPEs may be ovoid, pisciform or irregular in shape and may be surrounded by a pale gray halo or an adjacent depigmented linear streak (Fig. 47.2). They vary in size, from dot-like lesions to multiple disk diameters and position.

Fig. 47.2 CHRPE lesions in a patient with familial adenomatous polyposis.

Congenital grouped pigmentation of the RPE

Congenital grouped pigmentation of the RPE is characterized by small, darkly pigmented, flat, circumscribed lesions at the level of the RPE that generally increase in size as they approach the retinal periphery. The lesions resemble animal tracks (“bear tracks”) (Fig. 47.3). They do not affect vision; electrodiagnostic and color vision testing are normal. Mostly, lesions are unilateral and sectoral. Occasionally, the entire fundus may be involved.¹⁰ A depigmented variant (“polar bear tracks”) has been described in a sibling of a girl with normal bear tracks.¹¹

Fig. 47.3 Congenital grouped pigmentation (“bear track”). Unilateral, multiple brown patches in the retinal pigment epithelium of no functional significance. Fluorescein angiography shows masking of the underlying choroidal fluorescence.

(Professor A. C. Bird’s patient.)

Congenital simple hamartoma of the retina

These solitary, rare lesions differ from congenital hypertrophy of the RPE and RPE hyperplasia. They are typically located close to the fovea. They are circumscribed, nodular, and heavily pigmented, arising from the RPE and projecting into the vitreous through the full thickness of the retina. A feeder arteriole and venule are usually present. Subtle surrounding retinal traction may reduce visual acuity. Ultrasound shows a nodular echogenic mass with moderate to high internal reflectivity. Fluorescein angiography demonstrates non-fluorescence with a late, variable, surrounding ring of hyperfluorescence.¹³ The lesion blocks indocyanine green choroidal fluorescence. OCT shows elevation of the retina at the lesion with enhanced reflectivity of the vitreous face of the lesion and optical shadowing of the retina and choroid.¹⁴ The lesions are congenital, stable, and asymptomatic throughout life; intraretinal hemorrhage adjacent to the lesion and intraretinal exudation can occur.¹³

Torpedo maculopathy

Torpedo maculopathy, or paramacular coloboma, is characterized by an ovoid, sharply defined, non-pigmented lesion in the temporal region of the macula, centered on the horizontal raphe (Fig. 47.3). Lesions are longer horizontally (2–3 mm) than vertically (1 mm) with a characteristic point aimed toward the fovea and either a frayed, pigmented tail or rounded temporal margin (Fig. 47.4). Usually unilateral and solitary, satellite lesions may occur. The margins are sharply defined by a hyperpigmented border.

Fig. 47.4 “Torpedo” maculopathy. Sharply defined, non-pigmented lesion in the temporal region of the macula with a characteristic point aimed toward the fovea.

OCT reveals absent RPE, overlying retinal disorganization and thinning, irregularity and degenerate photoreceptor outer segments.¹⁵ Autofluorescence imaging shows hypoautofluorescence within the lesion.¹⁶ The foveal architecture and visual acuity are normal.

Retinal astrocytic hamartoma

Retinal astrocytic hamartomas are benign glial tumors of the retinal nerve fiber layer frequently associated with tuberous sclerosis (see Chapter 65). Calcification can cause diagnostic confusion with retinoblastoma, although the mean age at diagnosis of retinoblastoma is around 2 years, whilst that of astrocytoma is 14.5 years.¹⁷ Progression from flat to nodular lesions can occur. Most lesions range from 0.5 to 5 mm in diameter. They are slow growing, but very occasionally exhibit more aggressive growth resulting in retinal exudation, vitreous hemorrhage, retinal detachment, retinochoroiditis, neovascular glaucoma, vitreous seeding,¹⁸ and globe perforation.¹⁹

TSC is associated with mutations in one of two tumor suppressor genes, Hamartin (TSC1) and Tuberin (TSC2). The encoded proteins form a cytoplasmic molecular complex that controls cell growth and survival signals conveyed through the P13K signal transduction pathway.²⁰

Retinal capillary hemangioma

Retinal capillary hemangiomas (RCH), more correctly hemangioblastomas, are circumscribed, orange–red, round, vascular tumors with a prominent feeding and draining vessel (see Chapter 65). When sporadic, they are usually unilateral and unifocal. RCHs are a frequent association with von Hippel-Lindau syndrome (VHL, see Chapter 65), a multisystem, autosomal dominant, familial, cancer-predisposition syndrome. In VHL, the RCHs are often bilateral and multifocal.²¹ Fluorescein angiography shows early hyperfluorescence, late leakage, and distinguishes feeder vessels from draining venules; it highlights small peripheral RCHs, otherwise undetectable.²² B-scan ultrasound detects a mass lesion, measures basal dimensions, and detects subretinal fluid. A-scans show medium to high internal reflectivity.²³ OCT can measure retinal thickness at the macula and monitor treatment response.²⁴

RCHs are mostly located anterior to the equator usually superotemporally or, less frequently (10–15%), in the juxtapapillary region.²⁵ Peripheral RCHs increase in size gradually with surface glial proliferation resulting in striae and traction. Visual loss occurs from leakage and exudation leading to cystoid macular edema, exudative and tractional retinal detachment.²⁶ Neovascular glaucoma or cataract may occur.

Juxtapapillary hemangiomas are typically located temporal to the optic nerve. They may be sessile, usually endophytic or sometimes exophytic;²⁷ they may remain stable for prolonged periods. This, together with close proximity to the optic nerve and the high likelihood of visual loss from nerve damage as a result of treatment, has led to many advocating observation until the macula is threatened by exudation and visual loss.²⁷

Cavernous hemangioma

This rare congenital vascular malformation (hamartoma) of the retina is usually sporadic, occasionally autosomal dominant with incomplete penetrance. Retinal lesions are unilateral and unifocal and, while often isolated, can be associated with intracranial or cutaneous cavernous hemangiomas: a neuro-oculocutaneous phakomatosis.³⁴ Cavernous hemangiomas consist of saccular aneurysms resembling a cluster of grapes anywhere in the inner retina following the course of a retinal vein (Fig. 47.5). Visual loss may occur due to recurrent vitreous hemorrhage or macula involvement. Those located at the optic disk may compress nerve fibers.³⁵ Fluorescein angiography demonstrates delayed filling with hyperfluorescent capping of the saccules. No leakage or exudation occurs.³⁶

Fig. 47.5 Cavernous hemangioma of the retina showing the “grape-like” clusters of saccular aneurysms.

Combined hamartoma of the retina and retinal pigment epithelium

Combined hamartomas of the retina and retinal pigment epithelium (CHRRPEs) are rare benign, usually solitary, unilateral lesions, occasionally bilateral.⁴⁰ They are congenital, described in infants as young as 2 weeks old.⁴¹ Many are non-progressive, but most present with reduced vision, metamorphopsia or strabismus, particularly with macular involvement.

Lesions are slightly elevated with a variable amount of pigment (Fig. 47.6

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