Retinal Pigment Epithelial Hamartomas in Familial Adenomatous Polyposis: New Insights Based on Multimodal Imaging of 233 Lesions.

Objective To describe the multimodal imaging characteristics of retinal pigment epithelial hamartomas associated with familial adenomatous polyposis (RPEH-FAP).Design Prospective, observational case series.Participants Twenty-four eyes of 12 patients diagnosed with FAP based on systemic clinical findings.Methods Multimodal imaging of RPEH-FAP lesions included: Ultra-wide field fundus photography, ultra-wide field fundus autofluorescence, enhanced-depth imaging optical coherence tomography (EDI-OCT) and angiography (OCT-A).Main Outcomes Measured Features of RPEH-FAP on multimodal imaging.Results The mean age of patient was 46.8 years (range 20-72 years). There were 8 females (66.7%), and all patients were Caucasian. Two hundred and thirty-three RPEH-FAP lesions were identified (mean of 9.7 lesions per eye, range 1-31). The superotemporal quadrant was the most commonly involved quadrant (36.1%). Most were outside the posterior pole (92.7%). The most common appearance were small circular pigmented dots (42.9%). Depigmented margins were seen in 113 (48.5%) lesions. The pigmented portion of the lesion was hypoautofluorescent in 93.3% of cases, and when present, the depigmented halos/fish tails were either isoautofluorescent (46.8%) or hyperautofluorescent (35.1%). OCT was obtained for 49 lesions. Mean sub-lesional choroidal thickness was not different compared with choroidal thickness 50μm outside the margin. The RPE was relatively thickened in 67.3% of cases. Retinal thinning occurs in the outer retina, with thinning or absence of the outer nuclear layer in 83.7% of cases and of the ellipsoid zone in 93.9% of cases. Hyperreflective retinal spots were seen in 14 cases (28.6%). Eleven lesions (22.4%) had an associated pigment epithelial detachment (PED). One lesion demonstrated a subretinal cleft. No lesion demonstrated cystoid edema or subretinal fluid. No OCTA signal was observed on OCT-A.Conclusions In this series, a mean of about 10 RPEH-FAP lesions were identified in each eye. RPEH-FAP are usually hypoautofluorescent with outer retinal loss on OCT and as such are similar to typical solitary Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE) lesions not associated with FAP. However, key features differentiating RPEH-FAP from typical solitary CHRPE are the higher number of lesions involving both eyes, bilateral involvement, presence of an iso- or hyperautofluorescent depigmented halo or fish tail and the absence of lacunae or cystoid edema. The presence of PEDs is a new finding.