Intravitreal foscarnet is an effective adjunct after systemic therapy failure in pediatric antiviral-resistant cytomegalovirus retinitis

This report describes the case of a school-aged male child with T-cell acute lymphoblastic leukemia who developed cytomegalovirus retinitis despite systemic antiviral therapy. The patient had a history of cytomegalovirus viremia that improved with intravenous foscarnet and oral maribavir; however, routine ophthalmic screening revealed new retinal whitening and hemorrhages in the right eye. Anterior chamber paracentesis confirmed intraocular cytomegalovirus DNA. Although systemic viral loads declined, the retinal lesions progressed toward the macula, prompting initiation of intravitreal foscarnet. Treatment was initiated with a 1.2 mg/0.05 mL injection under anesthesia, followed by 2.4 mg/0.1 mL injections administered twice weekly at the clinic. The regimen was well tolerated and resulted in stabilization and regression of retinitis without central involvement, with fundus photography demonstrating fading whitening and vascular sclerosis.This case highlights the importance of close ophthalmic monitoring in immunosuppressed pediatric patients with cytomegalovirus viremia and emphasizes intravitreal foscarnet as an effective adjunct when systemic therapy fails. Furthermore, it demonstrates the feasibility of administering multiple intravitreal injections in the pediatric population, underscoring the role of local antiviral delivery in preserving vision in cases of antiviral-resistant cytomegalovirus retinitis.