Atypical COQ2-Related Retinopathy in Identical Twins with Nephropathy Mimicking Intermediate Uveitis

To describe an atypical presentation of COQ2-related retinopathy in identical twins with nephropathy, mimicking intermediate uveitis with cystoid macular oedema (CMO).

Retrospective case report.

A 33-year-old man presented with bilateral vision worsening and suspected intermediate uveitis. Examination revealed vitreous cells, CMO, retinal microangiopathy, and severely abnormal electrooculography (EOG) with only borderline full-field electroretinography (ERG) changes. CMO worsened with topical corticosteroids but improved bilaterally after a single unilateral intravitreal bevacizumab injection, suggesting a systemic therapeutic effect. His identical twin exhibited very similar retinal and systemic findings. Whole-exome sequencing identified a homozygous likely pathogenic COQ2 variant (c.683A > G), confirming primary coenzyme Q10 (CoQ10) deficiency type 1. Both twins also had nephropathy consistent with focal segmental glomerulosclerosis (FSGS) but no neurological involvement.

This report expands the phenotypic spectrum of COQ2-related retinopathy, characterized by retinal microangiopathy, CMO, and primary retinal pigment epithelium (RPE) dysfunction with preserved rod function, in contrast to the typical retinitis pigmentosa-like phenotype. Recognition of this presentation is critical, as early CoQ10 supplementation may stabilize disease progression and prevent systemic complications. Genetic testing should be considered in young patients with CMO resembling intermediate uveitis, particularly when associated with nephropathy.