Combined Hamartoma of the Retina and Retinal Pigment Epithelium: The Contribution of Optical Coherence Tomography in Redefining Its Development and Natural History – A Case Series

Introduction: Combined hamartoma of the retina and retinal pigment epithelium (CHRRPE) is a rare, benign retinal tumor typically diagnosed in childhood and traditionally believed to involve the full thickness of the retina and the retinal pigment epithelium (RPE) from early stages. With the advent of optical coherence tomography (OCT), increasing evidence suggests that the primary origin of these lesions may lie within the inner retinal layers, with progressive outward extension over time. However, reports documenting very early-stage CHRRPE confined to the inner retina remain scarce. Case Presentation: We report two pediatric cases of early-stage CHRRPE diagnosed at a tertiary referral center. A 4-year-old and a 10-year-old boy presented with unexplained reduced visual acuity associated with anisometropic amblyopia or strabismus. Fundoscopic findings were subtle or barely detectable, with no evident pigmentation, fibrosis, or exudation. Multimodal imaging, particularly OCT, revealed increased retinal thickness, loss of normal foveal depression, and disorganization of the inner retinal layers up to the outer plexiform layer, while the outer retina and RPE were preserved. OCT angiography showed distortion of the superficial and deep capillary plexuses in one case. These tomographic features were consistent with CHRRPE and allowed exclusion of other differential diagnoses, including foveal hypoplasia and malignant retinal tumors. Conclusion: These cases illustrate the earliest OCT-detectable phenotype of CHRRPE, supporting the concept that the lesion originates within the inner retina and progressively extends toward the outer retinal layers. Our findings highlight the critical role of OCT in identifying subtle CHRRPE variants in children with otherwise unexplained amblyopia or strabismus and contribute to a better understanding of the developmental origin and natural history of this rare entity.