Of these, two previously reported cases had retinal degeneration; one patient presented complete uniparental isodisomy leading to homozygosity for a splice-site mutation in the RPE65 gene [24] while an other patient had uniparental heterodisomy, with partial isodisomy, leading to an homozygosity for a missense mutation in the USH2A gene [23]. Here, USH2A is linked to retinal degeneration.