Calcified Sclero-Choroidal Choristomas in Mosaic RASopathies: A Description of a New Imaging Sign

Abstract

PurposeTo evaluate the imaging and clinical features of unusual calcified lesions seen in the fundus of mosaic RASopathy patients. DesignSingle-center retrospective observational study. SubjectsTen eyes with calcified fundus lesions in 7 mosaic RASopathy patients. MethodsThe lesions were evaluated with fundus photography, oral fundus fluorescein angiography, B-scan ultrasonography, Magnetic Resonance Imaging (MRI), and Computed Tomography (CT) scan where available. Main Outcome MeasuresThe imaging characteristics of calcified fundus lesions were assessed. ResultsWe found seven patients with mosaic RASopathies, 5 males and 2 females (3 with Linear Sebaceous Nevus Syndrome, 3 with Oculoectodermal Syndrome, and 1 with Encephalocraniocutaneous Lipomatosis) with molecular confirmation in 5 cases, all 5 having KRAS-pathogenic variants. Calcified fundus lesions were identified in 10 eyes (bilateral in 3 patients), appearing as slightly elevated, creamy-yellow lesions around or adjacent to the optic nerve, extending supero-nasally; all but two of these lesions involved both the choroid and sclera, with two of them only involving the sclera at the time of examination. One case developed a choroidal neovascular membrane (CNV) necessitating intravitreal bevacizumab injections. All 7 patients had B-scan ultrasonography and the lesion appeared as a hyperechogenic area with an acoustic shadow posteriorly despite reduced gain. Five patients had MRI, and where fundus lesions were present, there was a focal defect in the sclero-choroidal layer. Four patients had a CT scan and all four showed calcifications affecting both the posteromedial sclero-choroid and adjacent medial rectus muscle. Two of these patients had normal eye movements, one had a unilateral fixed adducted eye and a vestigial fibrous medial rectus muscle seen in imaging and intraoperatively, and the fourth had marked exotropia with a right gaze deficit affecting both eyes. ConclusionsWe propose that the lesions seen in this cohort are calcified sclero-choroidal choristomas (CaSCCs) and should be suspected in mosaic RASopathies when creamy-yellow lesions are seen in the fundus. If identified, the possibility of choroidal neovascularization should be considered during follow-up. In all cases where a CT scan was performed, a novel sign of sclero-muscular calcification involving the medial rectus muscle was seen.