Supplementary Material for: Cytomegalovirus Retinitis in an Eye with Unilateral Retinoblastoma: A Case Report

Introduction
Cytomegalovirus (CMV) retinitis in the setting of pediatric retinoblastoma is exceedingly unusual. Here, we present the first reported case of CMV retinitis in an enucleated eye with retinoblastoma after chemotherapy in the western hemisphere.
Case Presentation
A two-year-old Hispanic male without a family history of retinoblastoma presented with a three-month history of right exotropia and right eye squinting. Clinical examination revealed dense white vitreous opacities in the right eye. Ocular oncology evaluation unveiled an exudative retinal detachment with vitreous seeds, subretinal seeding, and a tumor emanating from the retina in the superonasal quadrant of the right eye. The patient was diagnosed with unilateral Group D retinoblastoma and RB1 sequencing revealed a pathogenic variant with mosaicism. Treatment involved systemic chemotherapy, intravitreal chemotherapy, and cryotherapy. However, the patient developed a rhegmatogenous retinal detachment with diffuse vitreous hemorrhage and ultimately underwent right eye enucleation. Interestingly, histopathological analysis of the enucleated eye revealed concomitant CMV retinitis alongside retinoblastoma. After consultation with infectious disease, antiviral treatment was not initiated as the patient remained asymptomatic and maintained a recovered immune system. Repeat CMV PCR confirmed viral clearance. The patient received a prosthetic eye and continues to be monitored for retinoblastoma recurrence.
Conclusion
Clinicians should be aware of the potential for CMV retinitis to develop in retinoblastoma patients receiving chemotherapy, which may complicate clinical decision making and management. Timely identification of CMV retinitis in this setting may improve patient ocular outcomes and overall prognosis.