Retinal drusen as an extra-renal manifestation of C3 glomerulopathy

Introduction: C3 glomerulopathy (C3G) is a rare complement-mediated renal disorder caused by dysregulation of the alternative complement pathway. Retinal drusen-like deposits may occur as an extra-renal manifestation. Case description: A 34-year-old woman with a history of childhood-onset nephrotic syndrome was later classified as having C3G. She underwent living-donor kidney transplantation four years earlier due to end-stage renal disease. She was examined as she was experiencing bilateral blurry vision of long duration and left metamorphopsia. Best-corrected visual acuity was 20/20 in the right eye and 20/40 in the left eye. Fundus examination showed widespread bilateral yellowish drusenoid deposits involving the macula and mid-peripheral retina. Spectral-domain optical coherence tomography demonstrated multiple subretinal pigment epithelium elevations and irregularity of the RPE-Bruch’s membrane complex, while fundus autofluorescence showed mixed hyper- and hypoautofluorescent changes. Renal biopsy material demonstrated intense C3c deposition along glomerular capillary walls with negative immunoglobulin and C1q staining. Discussion: The shared susceptibility of the glomerular filtration barrier and the RPE-Bruch’s membrane complex to complement-mediated injury may explain this renal-retinal association. Retinal manifestations may remain unrecognised for years, even in kidney transplant recipients. Conclusion: Clinicians caring for patients with longstanding C3G should be aware of possible ocular involvement. Multimodal retinal imaging can disclose retinal lesions and help clinicians to evaluate vision-threatening complications.