ABCA4-associated retinopathy complicated by didanosine-associated retinal toxicity

Purpose To describe a rare case of severe central and peripheral chorioretinal atrophy in a patient with ABCA4 -associated retinopathy and prior didanosine exposure. Observations A 66-year-old man with a 20-year history of Stargardt disease and HIV/AIDS treated with didanosine for almost ten years in the late ‘90s presented with progressive bilateral visual loss and color desaturation. Best-corrected visual acuity was 20/400 in both eyes. Multimodal imaging revealed extensive retinal pigment epithelium and choroidal atrophy involving both the macula and mid-periphery, with macular thinning and structural damage confirmed on optical coherence tomography. The peripheral atrophy pattern was consistent with known didanosine toxicity, while the macular degeneration was typical of ABCA4 -associated disease. Genetic testing identified three heterozygous ABCA4 variants: one pathogenic nonsense mutation, one likely pathogenic missense mutation, and one variant of uncertain significance. Segregation analysis was not possible due to lack of parental samples. Conclusions and importance This case suggests that prior mitochondrial-toxic drug exposure may exacerbate the course of inherited retinal dystrophies, producing unusually severe panretinal degeneration. Clinicians should review medication history in patients with inherited retinal diseases and consider long-term retinal monitoring even years after discontinuing potentially toxic agents.