Case 8
Author and Editor: Adrian Fung
Figure 1a. Colour montage fundus photograph of the left eye reveals a flat pigmented lesion at the temporal equator.
A 64-year-old Caucasian male saw his optometrist for a routine eye check. Fundus photography revealed a pigmented lesion in his left fundus.
Case history
A 64-year-old Caucasian male saw his optometrist saw his optometrist for a routine eye check. Wide-field fundus photography revealed a left pigmented fundus lesion.
The patient had previously undergone uneventful LASIK surgery for myopia. He was otherwise well and there was no history of cutaneous melanoma or systemic carcinoma. He last smoked 18 years prior. There was no family history of ocular tumours.
Visual acuity was 6/6-2 in the right eye (OD) and 6/9.5-2 (pinhole 6/4.8-1) in the left eye (OS). On examination there was no ocular melanocytosis, iris heterochromia or cervical lymphadenopathy. Anterior segments were normal and both irides were brown. On fundus examination there was a flat, round, pigmented fundus lesion in the left temporal equator (Figures 1a and b). This measured 4.0X3.0mm and had a nasal halo of depigmentation. There was no associated orange pigment, subretinal fluid or drusen.
Figure 1b. Magnified view of the left temporal pigmented lesion.
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Differential diagnosis
The differential diagnosis of a pigmented fundus lesion includes:
- Choroidal naevus
- Choroidal melanoma
- Congenital hypertrophy of the retinal pigment epithelium (CHRPE)
- Choroidal metastasis
- Melanocytoma
- Ocular melanocytosis
- Simple (congenital) hamartoma of the retinal pigment epithelium
- Adenoma of the retinal pigment epithelium
- Adenocarcinoma of the retinal pigment epithelium
Additional history, examination and investigations
Fundus autoflourescence showed the lesion to be homogenously jet-black hypoautofluorescent (Figure 2). Spectral-domain optical coherence tomography showed the lesion to have mild thickening of the retinal pigment epithelium and loss of the outer retina (Figure 3).
Figure 2. Fundus autofluorescence shows the lesion to be homogenously jet-black hypoautofluorescent.
Figure 3. Spectral-domain optical coherence tomography demonstrates mild thickening of the retinal pigment epithelium with loss of the overlying outer retina.
DIAGNOSIS
Congenital hypertrophy of the retinal pigment epithelium (CHRPE).
Clinical course
The patient was reassured that the lesion is nearly always benign and did not require treatment. Follow-up was scheduled for 1 year.
Figure 4. Three weeks after initial presentation there has been resolution of the retinal pallor and cherry red spot. The retinal emboli is still present, and the optic nerve is becoming pale (compared with Figure 1). Cilioretinal collateral vessels are present at the disc.
Discussion
Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is a benign, pigmented lesion of the retinal pigment epithelium (RPE).(1) They are often found equatorially with a mean basal diameter of almost 5mm.(2) The lesion is pigmented in 90% of cases and has central lacunae almost half the time (Figure 4).(2) Most lesions show slow growth over many years,(2) and drusen is inhibited.(3) Histologically the RPE is hypertrophied with cell heights double that of normal, increased pigmentation and lack of lipofuscin.(4) This lack of lipofuscin fluorophore explains their striking homogenous hypoautofluorescence, as in this case (Figure 2).(1,5) On optical coherence tomography (OCT) there is thickening of the RPE (absent in lacunae), loss of the overlying outer retina (Figure 3) and the occasional subretinal cleft.(1,6,7)
The differential diagnosis of CHRPE lesions is wide, and listed above. Of note, choroidal naevi can be differentiated by their choroidal rather than RPE location on OCT or B-scan ultrasonography, mild thickening, frequent presence of drusen, “feathered” appearance and lack of lacunae.(8) Choroidal melanomas usually show extensive choroidal thickening and may be associated with subretinal fluid and orange pigment.(9)
In nearly all cases CHRPE lesions are benign. However, very rare cases of adenocarcinoma arising from CHRPE have been reported.(10,11) For this reason, ongoing surveillance is recommended. There has been much confusion in the literature between CHRPE and colonic carcinoma arising in patients with familial adenomatous polyposis (FAP). In fact, RPE hamartomas, not true CHRPE may be associated with colonic carcinoma and FAP.(12,13) These RPE hamartomas can look like true CHRPE but are characterised by pisciform (fish-tail like) appearance, bilaterality and multifocality.
Figure 4. Colour fundus photograph of a congenital hypertrophy of the retinal pigment epithelium lesion with central pale lacunae where the retinal pigment epithelium is absent.
TAKE HOME POINTS
- Congenital hypertrophy of the retinal pigment epithelium (CHRPE) lesions are flat, pigmented fundus lesions which often have central pale lacunae.
- The differential diagnosis is wide and includes choroidal naevus and choroidal melanoma.
- CHRPE lesions can slowly enlarge over time.
- Key investigation findings are their homogenous jet-black hypoautofluorescence and loss of the overlying outer retina as visualized by optical coherence tomography.
- CHRPE lesions are nearly always benign. Extremely rarely adenocarcinoma has been described to develop from them.
- Hamartomas of the retinal pigment epithelium (RPE), not true CHRPE, can be associated with colonic carcinoma in patients with familial adenomatous polyposis.
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