Late Cystoid Macular Edema Following Treated Bilateral Endogenous Endophthalmitis Due to Klebsiella pneumoniae: A Case Report

Endogenous endophthalmitis (EE) is a rare but potentially devastating intraocular infection resulting from hematogenous seeding of an intraocular pathogen from a distant infectious focus. Klebsiella pneumoniae is an increasingly recognized causative agent, classically associated with hepatic abscesses, particularly in Asian populations, but with a growing incidence worldwide. Despite adequate treatment, late inflammatory complications may occur; cystoid macular edema (CME) as a delayed sequela of treated EE has been rarely described in the literature. We report a 64-year-old woman with no prior ophthalmic history and a documented penicillin allergy who presented with bilateral EE secondary to K. pneumoniae hepatic abscesses. At presentation, visual acuity (VA) was counting fingers at one meter in the right eye (RE) and no light perception in the left eye (LE). Treatment included intravenous (IV) imipenem, ciprofloxacin, and metronidazole, combined with bilateral intravitreal injections of vancomycin and ceftazidime. Microbiological analysis of hepatic drainage fluid confirmed K. pneumoniae on day 5. At discharge, RE VA recovered to 8/10, while the LE required evisceration due to irreversible functional loss. Two months later, the patient presented with a sudden drop in RE VA to 1/10. Macular optical coherence tomography (OCT) revealed confluent cystic intraretinal spaces with a central macular thickness (CMT) of 620 μm and a macular volume of 11.35 mm³, consistent with inflammatory CME. After confirming infection control, two posterior sub-Tenon injections of triamcinolone acetonide (40 mg/1 mL each), spaced one month apart, resulted in significant edema regression (CMT: 408 μm, average thickness: 341 μm) with VA improvement to 6/10. This case illustrates the occurrence of delayed CME as a late complication of treated EE, likely sustained by persistent subclinical inflammation mediated by pro-inflammatory cytokines (vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α)), disrupting the blood-retinal barrier (BRB). Sub-Tenon triamcinolone acetonide proved effective and well-tolerated. Prolonged ophthalmologic follow-up with systematic macular OCT is warranted after treated EE to enable early detection and management of late inflammatory complications such as CME.